I think the metric isn't "writing speed" but something more like "effort". The ideal path is zero-effort: brain to code. Trying to get as close to that ideal as possible is the goal. Going through VSCode (the LCD of developer tools) is of course going to be slower than going through your custom neovim setup - not because it's neovim, but because it's customized to the way you think about doing development. Going through AI may or may not be faster, since you still have to explain what you want to the AI: consider the time/effort difference in invoking your neovim unit-test tools vs asking AI to do the same thing.
I think the metric isn't "writing speed" but something more like "effort". The ideal path is zero-effort: brain to code. Trying to get as close to that ideal as possible is the goal. Going through VSCode (the LCD of developer tools) is of course going to be slower than going through your custom neovim setup - not because it's neovim, but because it's customized to the way you think about doing development. Going through AI may or may not be faster, since you still have to explain what you want to the AI: consider the time/effort difference in invoking your neovim unit-test tools vs asking AI to do the same thing.