GPU and CPU Light Baking

Having some differences I can’t explain while using 4.26 GPU lightmass bake vs CPU.

GPU bake seems to make everything a bit brighter and filled out than CPU (pics attached). Is this to do with it using ray tracing in the process that CPU doesn’t?
Second to this I have some movable objects like doors in the static environment(pics also attached). Using GPU bake the volumetric lightmass doesn’t seem to respect these movable objects like CPU does. I noticed the volumetric spheres are a lot less on GPU bake and I don’t know why that is.

Help appreciated.