So more questions.
Any opinion?
how would I install a smart switch in the scenarios in the picture linked aka that has 5 switched together
what is the best way to fix when 2 switches power on 1 light?
Thanks
There are literally dozens of threads in the forum already on exactly this issue, and people become very passionate when taking one side or the other. But the short answer is simple: both smart bulbs and smart switches have pros and cons, and it just depends on the details of each situation. Sometimes one is better, sometimes the other is better. Many people, myself included, use some of each.
If you do your own wiring installation, then, as you mentioned, smart switches will often end up being less expensive, although now that you can get dimmable white smart bulbs for about $15 each, that is no longer as true as it used to be. 
But there are certainly a lot of advantages to switches. The main reasons to use bulbs are:
One) you want the color changing features
Two) you want to create zones in a room where multiple fixtures all operate on the same branch circuit from the same light switch. These are commonly big rooms like basements, but sometimes also kitchens.
Three) you are renting and are not allowed to replace any of the light switches.
But if none of those apply, switches will probably be better.
So it’s just something to evaluate case by case. Don’t let anyone tell you that bulbs are bad because people will turn off the power at the wall switch- these days there are now several different ways to address that issue.
Sometimes bulbs are best, sometimes switches are best, budget will factor into it, so it’s just something you have to evaluate for yourself for each particular location.
As far as your specific questions, I’m not sure I understand. You could use either one smart bulb or one smart switch in the example that you give, although you might have to put switch lock or switch cover on the switch that controls a smart bulb. This option is discussed in the FAQ I linked to in my previous post.
You can also just use a smart rocker auxiliary switch, another option already discussed in the FAQ that I linked to and it will look just like the regular switches next to it. This is another very popular option.
https://www.amazon.com/Gocontrol-Z-Wave-3-Way-Accessory-Switch/dp/B00EAY3K5Y
Or if you don’t need a wall switch and you just intend to use voice or a motion sensor to control the smart bulb, you can just put a childproof lock on the switch for the bulb.
As far as a three-way set up where there are two switches each controlling the same light fixture, that can be handled again either with smart bulbs or smart switches with dumb bulbs. 
So there are lots of options, all of which have been discussed many times in the forum. Just start with the two links I already gave you and they will also link to other threads where you can find even more information.
jdroberts has covered a lot of this, but here’s my take:
you could use 4 smart bulbs and keep the dumb switch or remove it, wire it to always on and put a plate over it, or one of the other examples roberts gave.
OR, if you consider the goal as to adjust the level of light, then use dimmable bulbs and put a smart dimmer switch in. Rather than individual control of each light, you make each light put out less.
Depends on your exact need and desire for control. I prefer switches.
I’m not sure what you mean by “switched together”. My assumption is that a 5 gang with 5 switches leads to 5 independent lights/devices. They reside in the same gang box but otherwise have nothing to do with each other, right?
Personally, I use smart bulbs Because I am not in my final house. We are still in a starter house. And I don’t want to spend money and install smart switches in a house that I’m not gonna stay in forever. So for now, I will use smart bulbs and take them with me when I move.
When we move into a different house and I know we’re not likely to move again, then I might install smart switches.
My biggest problem is here. Sorry if my indications are not good. I really have a hard time understanding all.
So this new house we got here has ALOT of lights.
Like 30-35 bulbs total. The good news is that Philips hub can support up to 50. Now let’s try to get this as clean as possible.
There’s slot of fitting for lights and it’s hard to understand all.
Inside the house a lot of them are standard a19.
But we have a lot of PAR20 and possibly cri80+
The girl hates those lights and plan to change them at some points but no idea when. So for now we are stuck with those dumb lights.
But if we do change them I’m not sure philips hue does par20 and cri80+.
Even if they do I need 30 bulbs and some Philips hue dimmer (not everyone in the house is voice user).
But now if I get other lights like sengled I need a dimmer for those, which comes to either a smart switch which can be pricey.
As for thé outside of the house. We tried to install a smart bulb but we saw that the switch powers on another light ( which is a big rectangle light) no idea how it’s called. So if I put a smart bulb then the rectangle light will be on 24/7 which is why I was thinking about a smart switch. But inside it’s 5switch tied together so if change the switch inside we need one of the same size to fit with the other 4
Hope my point was clear enough
My philosophy has been pretty simple and served me well:
Exception…
3) If the light is in a lamp that is plugged into a socket controlled by a wall switch, use a bulb.
First let’s just talk about bulbs.
Bulb Codes
“A19” and “PAR20” are descriptions of the size and shape of the bulb.
The letter is the shape and the number is the size.
There is a separate code which describes the type of base the bulb has.
https://www.topbulb.com/light-bulb-bases
CRI
“CRI” is a completely different kind of measurement. It refers to the “color rendering index“, or how close the light is to natural light. The higher the number, the closer the color is to natural light. Unfortunately, it’s not a very accurate measurement, so most light bulb manufacturers don’t even print this value on their boxes. 
These bulbs might all have the same CRI value:
Usually people don’t care about the CRI value when they’re buying bulbs unless they are using the bulb as a spotlight for artwork.
So what you need to find out is the bulb code for the outside light. Not its CRI value. That will tell you what model bulbs you can use to replace it.
Outdoor Hue Bulbs
Hue has announced that they will have some new outdoor models available in a few months if you want to wait for those.
As far as The situation where you have five switches next to each other and only one of them will control a smart bulb, I already gave you that answer in my post above.
There are two different kinds of devices you can use for this situation.
The Sylvania dimmer switch is a smart switch cover. It uses batteries. It fits right over the top of the existing switch. It works well with smartthings. The only problem is the look as it is a very different looking switch than the ones it will be next to. If smartthings is not working, you can just lift up the device and use the original switch.
The other option is to use a switch which looks just like a regular rocker switch. It gets wired into the wall just like a regular switch. But it does not turn the current on and off to the bulb. Instead, it sends a message to the hub which then sends a message to the bulb. So as long as smartthings is working, switch will work. But if smartthings is not working, the switch cannot talk to the bulb.
https://www.amazon.com/dp/B00EAY3K5Y/ref=asc_df_B00EAY3K5Y5431213/
Kelvin scale to describes light bulb color. Like 4k Kelvin is my preferred color lights. I hate yellowy 2800. Looks like smoker lived there.5k is a little too clinical and shadowy imo.
I always buy switches if there’s more than one light or if a switch is there already, otherwise bulbs. If there’s a switch there already, you’ll have to bypass it or something anyway because people will turn off the switch!
CRI is color accuracy of viewed objects. Kelvin is the color of the light.
What is color temperature?
Color temperature is a way to describe the light appearance provided by a light bulb (lamp). It is measured in degrees of Kelvin (K) on a scale from 1,000 to 10,000.
Typically, commercial and residential lighting application Kelvin temperatures fall somewhere on a scale from 2000K to 6500K.
A light bulb’s (lamp’s) color temperature lets us know what the look and feel of the light produced will be.
The color temperature of a light bulb (lamp) is assigned using the basis of correlated color temperature (CCT).
For example, if you heat up a metal object, the object appears to glow. Depending on the Kelvin temperature that the metal object is being heated at, the glow will be various colors, such as orange, yellow or blue. The color temperature of light bulbs (lamps) is meant to replicate the Kelvin temperature of the metal object.
What color temperature is right for me?
Understanding Kelvin temperature (K) makes it easier to choose lighting that gives you the look and feel you want.
Warm White (2000-3000K) - Cool White (3100-4500K) - Daylight (4600-6500K)
At the lower end of the scale, from 2000K to 3000K, the light produced is called “warm white” and ranges from orange to yellow-white in appearance.
Color temperatures between 3100K and 4500K are referred to as “cool white” or “bright white.” Light bulbs (lamps) within this range will emit a more neutral white light and may even have a slightly blue tint.
Above 4500K brings us into the “daylight” color temperature of light. Light bulbs (lamps) with color temperatures of 4500K and above will give off a blue-white light that mimics daylight.
The Color Rendering Index (CRI) is a scale from 0 to 100 percent indicating how accurate a “given” light source is at rendering color when compared to a “reference” light source. The higher the CRI, the better the color rendering ability. Light sources with a CRI of 85 to 90 are considered good at color rendering.
Color Rendering Index (CRI) | Topbulb
A wifi plug should also be involved in this topic.
That’s a good question! WiFi plugs are often inexpensive to buy which is good. However, they use significantly more energy to operate over a year, they take up an address slot on your router, and they don’t help strengthen the mesh for your battery-operated sensors and locks. And of course most of them don’t have direct integration with SmartThings.
They can be a good solution for some people in some rooms, but most people using SmartThings, which is who this forum is for, will probably choose zigbee and/or zwave for a whole house solution.
In this case the OP has mentioned 35-50 devices. Many home WiFi routers only handle 32 devices, and that includes all your mobile phones, tablets, laptops, game players, streaming boxes, etc.
WiFi is great for a lot of things, including streaming audio and video, but for serious home automation the other protocols are usually considered first.
The exception is if you want a smart plug you can reboot even if the smartthings hub is not working. Many people use a single Wi-Fi device for that purpose. Choice is good.
See the FAQ (this is a clickable link):
Thank you for your insight!
Btw, do we really need to care about the energy costed by Wifi. It’s typical just 80mA x 5V = 400mW, much less than our fridge, bulb, thermostat etc.
Some people will care, some people won’t.
My house is solar-powered: we care about every milliwatt. 
Others care on general environmental or engineering principles: why use more energy than you have to?
But many people won’t care about the energy usage differential except for batterypowered devices.
Just another one of those areas where different people have different priorities.
I quoted that bit because I think it’s a source of confusion. I don’t have pics handy like jdroberts does. but I suspect our OP isn’t familiar with wiring.
in the US, switches are generally the same size and are mounted in a gangbox which is a plastic box mounted to a stud in the wall with wiring run into it for the switch. a 1 gang box holds 1 switch. a 5 gang box holds 5 switches. If you buy a smart switch, the body is bulkier than a dumb switch, but it fits in the space of 1 switch.
I won’t say you’ll have no trouble fitting a smart switch amidst the 4 dumb switches in that 5 gang box, but it CAN fit. The biggest problem is bending wires out of the way without uncoupling them.
