Google VR supports Android, iOS, Windows, Mac and Linux whereas the Oculus plugin only supports Windows, Mac and Android. Both can be used on the different headsets available (HTC Vive, Oculus Rift, GearVR).
The Google VR plugin is already bundled with FMOD but you will need to activate it in Unity by adding “gvraudio” into the plugins section in Unity’s FMOD Settings.
If you are developing for PSVR you will need to use the 3D Object Panner, which only supports PSVR and Dolby Atmos.
Due to the need for different spatilizer plugins, you will need two separate FMOD projects - one for desktop (Oculus and Vive) and one for PS4. We are working on improving this workflow for future releases.