Plex chromecast audio - choose device or set default

Hi folks

I have Plex running for my music library playback and currently cast to chromecast audio devices or a group.

My only limitation at the minute is having playback default to a device or the group (either would be fine as I can turn the amps off on the group or choose which to power up on my dash/front end).
To cast to a device you have to do it via chrome or the Plex iOS/android apps.

I’ve searched the Plex forums with no luck.

Could HA possibly achieve this with some sort of command or api calls etc? As anybody done anything like this? I was using mopidy and volumio for a while but found it unreliable.