I’m pretty relaxed about it when it comes to my son’s toys. My son’s room has legos all over the floor right now, but he plays with them everyday. He likes to build different things and then play with those for a while and then build something new. There are times when I make him pick them up (so I can vacuum or if we have company coming for example), but most of the time I let him keep them out, as long as they stay in his room.
Food is a different issue though. He is only allowed to take a snack/drink in his room on special occasions and he knows the dirty dishes and trash must come out of the room as soon as he’s done with them.