the old ui widgets can't really (I assume) vary that much in properties or location (the layouting is stricter and will break if you push it too hard)

It would dynamically calculate a minimum window size based on the components inside and you could then resize the window as you wanted with things calculating and resizing as you go, adapting to font selections and themes.

The actual implementation is archaic by todays standards but it did use attributes on UI objects to determine min/max sizing and other things, similar to CSS in concept.

Sadly no font sensitivity on display (possibly because Amiga owners take it so much for granted that they don't think of it as special), but it shows what MUI can do in terms of GUI elements, window resizing, etc.

After leaving the Amiga for Windows, the three biggest things I hated about its GUI were all those endless non-resizeable windows, the complete lack of font sensitivity, and the horrible scrollbars that didn't show your actual content size (and that snapped back if you moved out of some invisible box). And here we are, twenty years later, and nothing has improved at all...