Mapping with Cube Grids.

Hi,
I’ve been trying to find information regarding best practices for mapping with the Cube Grid tool. My main question is if you are building for instance a multi-story building, would it be best performance wise (FPS game) to generate larger cube grids (one per floor) with walls, floor, ceiling in one mesh populated with smaller blocks for detail and architecture or is it better to create rooms literally block by block like in other editors?

I also often see people building their levels by instancing small blocks snapped together to create larger walls which I understand would reduce the number of mesh’s loaded but would also increase the number of rendered faces in an area. Not sure which is more costly.

And lastly when watching a tutorial on lighting I was told its best to make rooms block by block and when I make Cube grids too large I get large actor “pre-shadow” performance warnings when building lights.

Any advice is greatly appreciated, still fairly new to UE5 and would love some insight into more advanced users methods for performance geared level design. Thanks.