Hey there @Sgu welcome to the forums
I actually have those same speakers and am very happy with them, and I personally leave them on all the time. However as with most things it’s totally possible to do what you’re asking but will need a little work; and I’d be more worried about the complexity you’d need to introduce to do this causing more problems than leaving the speakers on.
We used to have functionality within balenaSound to toggle GPIO pins on and off when bluetooth devices were connected/disconnected, but I think this has been deprecated since balenaSound has expanded into a much more powerful application and handles much more than just bluetooth connections nowadays.
With those speakers (at least on my version), the power switch is a mains voltage rocker switch, and the power cable cannot be disconnected so the only way you’d be able to switch it short of dismantling the speakers and modifying them internally would be to switch the mains power input with something like a smart socket or introducing a relay inline that you could drive from the GPIO pins on your balenaSound device. Once you have this method set up it’d then be a case of figuring out how to hook into balenaSound to switch your socket or GPIO pin whenever audio started or stopped. As I said I don’t think this is supported today but you could add an issue on the repo and maybe consider adding that functionality to balenaSound too.
As for the volume I find that I can turn the volume up on the speakers to the maximum I would ever want to use and then control the volume from balenaSound, so that’s no problem.
I hope this helps with some ideas!