Is pairing efficient when the two developers use different editors (or even different keybindings)?
I feel my IQ drop by 30 points when I can't use my customized Emacs and I dont know if the benefits of pairing are enough to counter this.
The only thing you need after that is for both editors to automatically refresh when a file changes on disk. With Emacs, you can get that with "(global-auto-revert-mode 1)" in your init.el. You can make Vim auto-refresh too, though I'm not sure how.
At my previous job we had to get a QIDO[1] since I type Dvorak and switching layouts with Cmd-Space was driving us both insane. We would invariably forget to switch and either write gibberish into the file or, worse, hit some unintended keyboard shortcuts. After getting a QIDO it was fine though.