On the specific issue of window corner roundedness, Windows 11 is great IMO. The corners are rounded when the window is floating free, but change to square when it's maximized or snapped to a side of the screen. The perfect design.
I've never really needed that, or I don't understand the need for there to be a difference. I typically tile windows into each corner based on how large I need them. When I need more than 4, I'll manually place them.
What I do notice is the wasted space needed by the entire window border to accommodate rounded corners and how annoying it is to grab a window handle in e.g. Ubuntu w/ GNOME because you're clicking/touching where the corner would be (but isn't, because it's round).
