Which are both buggy and one of them is abandoned.
> Lem is a new editor written in Common Lisp that has slime "built-in".
"Lem" is not (neo)vim, has Emacs RSI bindings and even if by some chance it included some "vi mode", it would simply be an emulation, not an actual vi editor. Same issue with Emacs using "evil mode".
Lem supports vim key bindings, according to its README.
btw, I don't have any issues with emacs keybindings, but I chuckled at the "Emacs RSI bindings" :)
In fact, I think vim keybindings are superior for editing - you can't beat hitting "." to repeat an action - but after using emacs for ~5 years I find myself in it a lot more than I expected when I started using it. The whole thing with key bindings is that for whichever one(s) you use your muscle memory catches up.