Emacs just controls everything now. Why not!
Rather than using the builtin NixOS support for EXWM I've added a
custom snippet that takes care of the launching. This assumes that the
user launching the session has my emacs configuration installed, which
I, in practice, always do.
* remove setup of i3wm (until I'm comfortable using exwm I will keep
the i3 configuration files around)
* disable compton (exwm brings its own compositor)
* disable auto-starting of emacs user service
* enable & configure exwm (also see correlating commits in my emacs.d
repository)