WiFi bulbs don’t necessarily power on when power is restored after a cut; most zigbee bulbs do. Some people like this, assuming that the power outage represented a problem that they need to investigate. Other people hate it.
One community member has addressed the problem by creating a “Canary bulb” Smart app where if a particular bulb lights up when it’s not expected to, the app turns all the other smart bulbs in the house off. Again, some people would like that, other people would not.
You’re quite right that you have to have an RGBW bulb or LED strip in order to get color. Technically, it doesn’t have to be networked to get color, particularly the LED strips, but it turns out to be easier and typically less expensive these days to go with a networked device.
As far as switches to use with smart bulbs, see the following:
Phillips mentions this as a safety feature. If you have someone flipping the switch off/on 99% of people would expect lights to come on. I rarely have power outages (maybe twice a year?)
I actually purchased a smartswitch and hooked them up to my hue bulbs. Then realized that was a waste since I never used the switch. Instead i purchased a Hue Dimmer Switch, placed it where it made sense and reverting back to a dumb switch, leaving it on.
We mostly use white bulbs, but do have two RGBW lights (One in the living room, one in my housemates room) which we use for notifications.
For example, when I come through the front gate, the light in my housemates room comes on pale blue. Once I come through the door, I turn that light off again by voice. So if I get stuck in the yard, as sometimes happens, the blue light being on let’s my housemate know he needs to come help me. We found this method works the best. It doesn’t bug him when he’s playing video games the way a beeper might. But he also doesn’t ignore it when he’s playing the way he does with text messages.
So it’s a persistent but not annoying notification.