Hi Jony6234, The only way the extra LODs would decrease FPS is if you have removed intermediate LODs before the Billboard/Planar LODs and UE4 is rendering the LOD0 at further distances. You’ll need to just remove the lowest LOD’s and replace the “Screen Size” they were at. E.G if the lowest LOD in the mesh was at about 0.3 - make sure you specify 0.3 for the Billboard LOD once you have removed that one. The higher the ScreenSize, the closer the LOD appears.
Regarding the Building - the LODs for that should be created as Billboard rather than Planar.
I hope this helps,
Richard.