>>288737779
Map making works roughly the same but sometimes you actually want multiple meshes specially if you are duplicating a lot of it.

The most important part of map making optimization is the occlussion culling. You have to deliberately make it so people only see parts of your map at any given time. When the occlussion is baked on static objects, it makes the map so much much more fps friendly. That means occluding walls, terrains or objects are a good thing.