Okay,
There are no hard rules to a a good naming convention apart from being consistent…and even then, you can change your naming convention along the way, when something works better for you and/or people you work with. But try to be consistent (at least within a project!).
The Capitalization of Collections is very personal, I also try to use all lower case for Materials, so i can have something like this for instance:
This makes sense to me, so it’s a good convention for me.
Make as many (nested) Collections as you want/need! They are a great way of organizing your scenes.
You’ll develop your namings as you go, but you’re off to a great start! You’re not doing anything wrong!
And yes, the Collection Colors are fantastic; I should use them more often!