On SVC, there's a setting for the Default Service, which is global to the whole system and can't be set by speaker. This is the account which is being used to play the playlist.

When you set multiple Apple Music accounts in your system, you can give them different names, e.g. Mike's Apple Music, Mary's AM, etc.
You can try something like:
- Hey Sonos, play the playlist Likes on Mike's Apple Music
- Hey Sonos, play the playlist Likes on Mary's AM in the Living Room”