Working with levels

Hey,

I have been wondering about using levels. I use UE4 for Archviz purposes and was wondering if using multiple levels within a project would help with the overall FPS rate and file size?

Many of the projects I work need to be able to walk through the interior and exterior, by having these on different levels does this increase the FPS rate because the interior of the building for example is loaded onto a different level?

Im not quiet sure how it works. If anyone can explain or point me in the right direction that would be great.

Thanks.