I do use sonobus with some others in the Seattle area. Since I have the time and there is already a convenient Thursday mid-day session on Jamulus, I've started participating in that. I'm looking at running two instances of Jamulus, with the Helix driver set up on one and my regular "interface" ( mackie mixer) serving vocals and backing tracks to another instance of Jamulus. There is also a solution using Reaper's rearoute.
Then you have an approach using ASIO Link Pro -- too much info to digest :-)
But even just continuing with guitar/vocal/tracks through the Mackie only I've found that panning before sound hits Jamulus or Sonobus makes a big difference. When I was struggling to get IEMs dialed in someone pointed out the advantages of a stereo mix over mono. They likened mono to listening to six other musicians who were standing single file facing you. So first in line is the piano and it's too loud, so you turn up the level of the drummer who is 3rd in line. Then you can no longer hear the piano or others adequately, and on and on and on.
But if you can put the drummer and bass in your left ear, say panned out 50%, the piano and lead vocal in the right ear, etc etc and possibly also lower or even remove some sources you don't need, you can hear what you need at lower volumes.
In Jamulus etc you can't mute people because you won't hear them talking, unless they're using multiple sessions so you could mute their instrument if desired. ( or if they are panning ahead of Jamulus you could pan them in Jamulus to get what you need from them)
My brief experiment with this panning yesterday did make a big difference. It was in Sonobus but my vocal was totally in the left ear, with most of the guitar in the right and it made it easier for all of us to hear what I was doing more distinctly.