[Question] Can I use Armor Stands?

I'm making a map (or at least trying to) and I was wondering whether using Armor Stands is okay. Would they get de-spawned since they count as entities? Also is there anything else that should not be used in maps? Command Blocks and large Redstone contraptions are probably prohibited because they can cause a lot of lag, anything else?

Forgive me if this is in the wrong section.