VR and stationary lights

I’ve been using unreal for a while and just got into VR development. Read through the VR best practices and saw that it tells you to set all lights to static except for the sun, which apparently should be movable with CSM enabled. What i’m wondering though is: why is this? I have area shadows enabled on all stationary lights including the sun, would that make it any faster? As far as i can tell that makes them use regular lightmaps for static lighting? Seems to me like dynamic lighting with CSM would be a lot slower than this. I want a good balance between performance and quality, and i want it to have realistic soft shadows with still having the nice high quality specular and normal map response. Will having the sun stationary with area shadows have a huge performance impact or will it be fine for most systems?

EDIT: reposting this on the answerhub