The current version 1.3.2/3 has a bug in Auto, it will only adjust up. Use Initial Auto instead until the next update, or periodically reset the jitter buffers with the |< buttons.
Yes, there are plans for a headless standalone version on platforms where people want that. You can actually do it right now with Jambox pi dist, which includes SonoBus: https://github.com/kdoren/jambox-pi-gen
Yes, the iOS version does stay active in the background when connected to others. It should pretty much do what you want for this use case, but you will need headphones everywhere because this thing is focused on quality, and so there is no echo cancellation.
And I love AOO, I use it as the basis for SonoBus.... I’ve been meaning to contact you about it, and work on merging your latest into my fork (which has diverged a bit over the last few months).