Let’s address at least a couple of things, and I will leave the rest for others.
As of several years ago, the BRIDGE is no longer required. You can wire a standard player/speaker to your router, and it will function as both a speaker and a BRIDGE.
Also, if you’re still using a BRIDGE because you don’t have a speaker close enough to your router to wire, and you choose not to have your speakers hang off your normal WiFi signal, you should replace your BRIDGE with the newer, better, and certainly more robust BOOST. The BRIDGE is known to frequently have a failure of its power supply, which can cause very unusual and difficult to trace issues in the system, due to the fluctuation in voltage as it begins to fail.
Yes, the BOOST can run either S1 or S2, but not both simultaneously.
In your case, continuing to run in wired mode (either a speaker or a BOOST) is recommended, to allow the Sonos devices work off of Sonos’ proprietary mesh network, where each device reinforces the mesh. One does need to be careful not to run both WiFi and SonosNet on the overlapping channels.