I used exactly this setup before (mosh + tmux + Tailscale + VPS), so maybe I can help. Both tools are terminal UIs, so they fit naturally in what you have: you run them inside tmux on the VPS, and mosh handles the bad connection like it does for everything else. But honestly they don't change much when the connection is bad, because the UI still goes through the connection. This is one of the reasons I built ShellTeam (github.com/sebderhy/shellteam): the sessions stay on the VPS and the UI is a web app, so when I lose internet on a train I just reload the page and everything is still there. I'm obviously biased, but for intermittent connections I think a web UI works better than a TUI over mosh.