@DWillons
In generell it‘s possible to group rooms, even if audio source is tv mode of a soundbar.
But to do so with your old Play5 Gen1 all devices have to be set up on the S1 system. So you would have to buy an older soundbar model that also supports S1 like the Playbar, Playbase or Beam1.
https://support.sonos.com/en-us/article/sonos-app-version-compatibility
The other option (to use any soundbar you like) would be to switch to a S2 system by replacing your P5 ton a newer model.
Optical connections between TV and soundbar are possible but using the HDMI cable ARC option is almost always better if it is supported.
Grouped speakers will show a slight delay, 75 ms, when playing the TV source, which isn’t usually a problem in different rooms.