That's interesting. My problem is very similar to the issue I labelled [2] above --- where there would be more than a second of delay in interacting with some snippets.

But somehow this suggests to me that I might have been doing something wrong. I use vim+ultisnips+(your excellent vimtex) while you use neovim. Out of curiousity, do you specifically set your python provider for your neovim in your config?