I actually love having a small scrollbar. On Firefox, I have it as a tiny sliver that only shows up when scrolling.

  :root{
    scrollbar-width: thin;
  }

And:

  user_pref("widget.non-native-theme.scrollbar.style", 3);
  user_pref("ui.scrollbarDisplayOnMouseMove", 0);

in about:config

You can have minimaps enabled in Emacs and Firefox, but I don't see a use for them, to be honest.