Fwiw your question in 99% a Spotify question so you may find more fruit searching Spotify forums about this. By large Loxone is "just" a Spotify Play device and acts like any other manufacturer's device, when streaming playback from within the Spotify app.
One benefit you'll find of the family account is you can create one shared family profile in it and log the Loxone app in with that, so any shared music or podcast etc played through automations doesn't interfere with real user's profiles
Regarding adopting in (or migrating out) existing accounts to the family profile, this didn't used to be possible but last time I looked they'd significantly improved the family account management, but really this is where you'll find much more info from non-loxone resources :)
HTH