Emacs is my favorite software (I do "basically" everything in emacs, except I also use firefox) but how is exwm a ood idea? Emacs is single threaded... How did they solve this problem?
The answer is that they didn’t. If emacs freezes up, you just have to wait.
In reality this almost never happens. Besides - it is so lightweight - killing a session and starting a new one takes seconds.
Not sure what you mean? I don't use exwm but my emacs gets stuck e.g. when tramp-mode is connecting to ssh. This is not a problem for tasks I use emacs for, but if my entire OS gets stuck because I'm trying to connect a server, I'd get annoyed.
Maybe it's less of an issue because your window manager doesn't need to connect to ssh servers or even do any kind of heavy lifting.