I loved using cmux for several weeks until I saw the ram usage.
My cmux has been running with 136 workspaces and 218 terminals, and has been hovering around 5.7 GB. Granted, the theoretical RAM minimum for this number of terminals is around 1-1.5 GB before real scrollback, so we definitely have more work to do.
If it helps, the main reason I love cmux is how can I manage my projects into folders, I have fast access to all the projects which made my life a lot easier working in the terminal. I can also have coding, test, monitoring spilt in one tab per project.