XFCE note: autohide panel (the clock is not), accessibility WM tweaks turned on (hide title…) as I usually have a window maximized. Raise-on-focus (Window Manager settings, similar setting in tweaks for window cycling) turned off, allowing rolled-up windows to not disappear when unfocused.
System note: I have not maintained it well, broken dependencies right now and have finally got bit by nVidia as my system won’t properly wake from suspend. Getting an alternative is somewhat of a mess, especially prices and getting full performance.
I made this ultra-minimalist window theme a while ago (this is the second version, with the widget-capable layout and style-based color accent) and have been using it.
The title is 12px tall (the buttons are default 8px, though can get taller with alternate hover/click states).
At this size, XFWM has a design issue with font sizes/baselines so most fonts are cut off (the selected font is Nimbus Mono PS Bold 10, larger has text descenders cut because text can’t overlap window contents)
I would try to take this idea further (and fix some of XFWM’s other relevant issues) with my own WM but I use a somewhat niche language and couldn’t figure out how to render a rectangle the last time I looked into it (the WM I was looking at doesn’t have titles/window controls).
Not set on a name as lots of themes have size-based names but are not as minimal.
It was too slow for an edit, but this is the older version screenshot (note:Imgur only loads links for me with a private window)
One small benefit of the current layout is that I can see both edges of a rolled-up window (when focused).
I would definitely try more things if I had more control. Big text would be nice with content overlap (or outside window+outlined+noBG?), inset controls especially if dynamic. Maybe even different placements of title or buttons.