Should I be doing this with volumes?

I’m making a 2D game where play takes place in separate rooms.
Nothing can move between rooms ( except for the player ).
Currently I have LightMassImportance, NavMeshBounds and PostProcess volumes affecting only the room in the middle

Screenshot from my editor

I have no idea whether I should use 1 of each volume for the entire game world or 1 per room.

The world structure looks like this:
World ( only 1 ) → Area ( 10 in total ) → Room ( ~18/area )
All rooms have equal distance between each other and all are placed on the same plane.

I can’t find any information about how NavMesh Volume exactly works so info about that is also useful

So is this ok? Wouldn’t it slow the game to a crawl?