Is it currently possible to use FMOD Studio and Steam audio in UE 4.19?
We are currently working on releasing our integration for UE4.19 and should have that available soon.
The UE4 Steam Plugin will not work with FMOD, they are two different systems.
With FMOD, the plugin needs to be set up in Studio, then you would use FMOD to control the sounds in game.
The FMOD Steam Audio plugin is handled by Valve, you will need to contact them regarding development.