What really irks me are the autohiding scrollbars, especially when working over a VNC connection and I have to wait for them to fade-in over a 3000km link
Right, anything that's just mimicking the default without checking this setting is going to be stuck. Also anything more custom, like websites that override scroll behavior.
Website scrollbars can probably be fixed with a userstyle and the Stylus extension, but with apps using electron or other non-system UI library you're just stuck with mimic-scrollbars (though there are exceptions like Qt which does honor scrollbar settings).
Give me scrollbars and keep them visible please.