Fast and easy toggle between 2 input sources

I have 2 TVs side-by-side in my media room.  Currently they are both connected to an AV receiver on separate inputs. When I want to change which TV is feeding sound into the room’s speakers, I have a single button on my remote which simply selects the next favorited receiver input, which effectively toggles between the 2 sources.  (Note: this is useful when one TV goes to commercial so I want to temporarily hear the audio from the other TV)

I am thinking about upgrading to a full Sonos setup for the room’s audio and would like some advice for how to best achieve the same convenient audio source toggling.  I understand that I’ll be able to use the app to select any source to play in any room.  But is there a way to achieve a toggle like effect with a remote or smart home device?  If I have to use the app, how fast or easy will the transition be?

Here is my current thinking for the hardware setup.

TV #1 connected to an Arc soundbar via HDMI-arc.  The ARC will be joined to a sub (gen3) and an Amp driving a pair of in ceiling speakers for the surrounds.  That will be my default TV/movie playing speaker setup (room).

TV #2 connected to a second Amp via HDMI-arc. That Amp will power a second set of in ceiling speakers that will just be used for music playback.

The goal will be to toggle the Arc to use either its own HDMI input or the HDMI input on the second Amp.  I current have a harmony remote so ideally I’d be able to program a button on that to toggle the source, or maybe 2 buttons (1 to select each source).  I could also change to a different remote (or other hardware) if there is a better option.

Thanks for any advice, it’s hard to know how this will work without the actual hardware, and I don’t want to order the hardware until I know how it will work (catch-22).