> Ok, so what is the conclusion? kak is almost fine, at least better than vis?

I wouldn't say that -- the way vis does regex is pretty neat. I'd say all the editors have limitations. Vim is super efficient for global search and replace because after all these years it's still ex underneath, and ex is good at that kind of thing. Vis and kak choke on my ridiculous global search and replace test because they both want to create four million cursors at once. But on the other hand, vis needs the least memory if all you're doing is opening the file, and it seems pretty snappy for ordinary editing tasks. I'm sticking with kak because I'm addicted to selection-oriented editing.