What makes Linux appealing to me is the extent of customizability, but I didn’t find many answers when looking up with desktop environment is them most customizable. Some say KDE is most customizable than say, Gnome, but doesn’t Gnome support CSS customization while KDE doesn’t?
Nothing is stopping you from making a terminal with a very niche command running on the background 24/7 and call that a “window bar” btw, so… as long as its a minimal installation, “they sky is the limit”. :^)
In terms of DEs nothing comes close to KDE.
Last I saw deepIn wasn’t far off. But it’s always been a similar project to KDE in many ways. (QT based, complete ecosystem including desktop and apps) Though they have had some rather staggering refactors between versions.
Deepin is quite beautiful but I don’t think it has that much customization.