Not that it's by any means a full answer, but I did notice on one of the Fextralife vids that the toolbar had been expanded, though upwards rather sideways, so looks like that might be resizeable. Which would be good for me, to be able to get most of my commonly used actions/items on the front screen.
Personally I never do and never want to play BG2 with no HUD like that (I've tried briefly in the past but just feel kind of exposed and as though I don't have visibility or control!), and hiding or shrinking elements is never something I've wanted to be able to do in BG3 either. In fact I tend to expand the combat log, that is hideable. I reckon everything fits pretty neatly, with the central space enough generally to see what's going on with what I'll always think of as the "extra space" of my widescreen monitor at the sides used for things like the minimap and combat log on one side and my party on the other. And easy access to common commands down the bottom. Which is not to say that I think it's by any means perfect, but my preferences would tend to run in the direction of more rather than less!
One big thing is that in late 90s/2000 people mostly had 15 or 17inch 4:3 monitors...So I guess it makes more sense to have an option to clear everything to get the most screen space for exploring (plus the above shot uses the widescreen mod@1280x800...giving even more area compared to the original max 1024 or 800x600).
