At our place, the grandchildren sometimes sleep and chill in the bedroom as well. And are allowed to go to the wardrobes.
Then you should just knock anyway. I think, as long as this isn’t a 10-person anarchist shared flat, you can manage to know where each resident is or where you might need to “be careful.” For many, the doors are open anyway, and if they are actually closed, you ask if it’s okay to come in. The house is very compact. It’s not small, but with the desire for a large more or less separate living area, then the third “bathroom,” the need for a separate office – it can get a bit tight. If you take a youth bed 120 cm wide, then an appropriate desk, there’s not much left for personal sports equipment. You don’t store suitcases and decorations outside (this also means the storage room behind the garage), and constantly going up to the attic can be a burden.