welcome! 
You’ll probably get more people helping you with your automation questions if you post those in the automation section of the forum. Go ahead and start a separate thread for each use case, that will get you the best answers. Start your threads in the following section and put the topic title in the form of a question and you will get lots of responses. 
In most cases there will be at least seven different ways to do each automation, and everybody has their own preferences. That’s one reason you want to put each use case in a separate thread, it may be that one of the different methods is more applicable to a particular use case.
The seven methods are:
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The official smart lighting feature. This is the only option which will run locally except for some bits of STHM. So a lot of people will always start with this and see if they can do what they want there. to get to it, you start with the three horizontal line menu in the upper left of the app, then choose smartapps, and then choose smart lighting.
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Smartthings home monitor (STHM)
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scenes
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official automations (this is the rules engine you get to if you choose “add an automation“ in the app)
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The official rules API. This is new and still a work in progress and not many people are using it yet.
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WebCore. Very popular for complex automations and some people end up using it for everything. This is essentially a scripting language for smartthings which was developed by the community. Some people use webcore for everything because they’re used to it and because it’s the only option that lets you back up your rules.
(Here’s the short FAQ. The topic title is a clickable link.)
- Custom smartapps. Back in 2017 we used to use these a lot, The official features were pretty limited and webcore didn’t exist yet. There are still a few that are popular for specific use cases, but these days the official features do a lot more, and webcore does everything, so individual custom smartapps just aren’t needed very much anymore. But somebody may still recommend one if it happens to be a perfect fit for a particular use case. @rboy ‘s Apps are a good example of these. His are very complex with a ton of features And are highly popular for those willing to pay for a third-party license fee. There isn’t anything that comes close to his lock management options, for example.
Confused yet? 
we often say smartthings is very powerful, but not very discoverable. So hang in there, ask questions if you get stuck, you’ll figure it out.
Anyway, as far as your sunset to sunrise question, that’s very easy if you use the smartlighting feature.
