Why is this a worry for you?

Since any combination of SONOS Rooms can be members of a Group, all sources of online music can be played in any combination of rooms. As far as the music service is concerned, the group is a single stream.

Perhaps the concern is the limitation on the number of concurrent streams permitted by the streaming service for independent music play in each room?

• Google Music is dead.
• YouTube Music’s Sonos integration is terrible, see many other threads.
• Spotify works fine.

There are ~sixty other music services to choose from, depending on your location. You should be able to find something that works for you, regarding content quality, cost and user experience.

Some limit multiple streams.  I’m not concerned about a single stream.  What about when my wife is in the bathroom listening to Elton John, I’m in the office with smooth Jazz, and each of my two sons are in different areas of the house wanting to listen to their preferences.

I may need to try spotify again.  Can we listen to, say 4 or 5 different streams at the same time?

Yes, Spotify treats a Sonos household as a single endpoint. In my experience most do, though I recall SiriusXM NOT doing so, but I quit using that for other reasons.