Most effects should be possible with VR. It’s hard to say how easy it would be to fix without knowing how the distortion is implemented though. Many effects are directly mapped to the render target UVs which don’t correspond well to the VR field of view.
There is always some performance cost on post processing effects, but there shouldn’t be any problem running them on PC at least. AFAIK they are heavy on mobile applications though, and if I remember right, require the Mobile HDR feature to be enabled.