You can always assign them to rooms even if you just have one room. But I think groups would work for your case. Like say put all your actual lights in the actual group. And then say “turn on actual lights.”
Scenes..I can’t really figure them out. They seem way too complex for what I want to do, which is to turn things off and on.
Scenes are activated, they don’t have direction, they don’t work at all for turning things in and off, instead you have to create separate on and off scenes.
HomeKit should really support overlapping groups, it is a feature I also miss. But as a hack you could use rooms as a secondary group mechanism since you don’t need them to represent actual rooms.
Scenes..I can’t really figure them out. They seem way too complex for what I want to do, which is to turn things off and on.