> Is this the equivalent to calling ~avy-goto-char-timer~ (from a keybinding) whenever inside Helm completion windows?

Yes it's exactly the same: I'm actually reusing the same shortcut for both. In a regular buffer I'm using precisely avy-goto-char-timer and in, say, "counsel-find-file" (which I use instead of "find-file"), that same shortcut calls the ivy-avy function.

Now I use ivy/counsel/swiper/avy but don't use helm so cannot help there.

P.S: and I confirm I just hit the letter and, say, the file immediately opens (I don't need to hit enter for example)