Hi gmittal,
nice that you finally have your stuff together.
To your first question:
The installer probably made a 'speakers group' with all (!) speakers associated/assigned to the tv command/button - for watching and listening to tv.
However you can make up to 9 different 'speaker groups' and choose them manually - just as you please and need it.
And you - yourself - can change, what was programmed as the default group to another one, if you prefer that.
Didn't the installer inform/instruct you how this works???
Please do consult the user guide, which you can find online on the B&O homepage.
N.B. You can create a default speakers group individually for each of the sources on the tv - such as one with the two fronts and the sub for music listening through Spotify.
You certainly don't have to turn off the speakers by the mains!
Location: Flensborg————Danmark