That would sound like a self inflicted wound. Personally I really loved emerald the window decorator along with compiz.
emerald, compiz: fairly famous window managers/compositors everyone used to use, e.g.
https://www.youtube.com/watch?v=4QokOwvPxrE
> how is this related to window borders
compiz is famous for including all sorts of fancy/over the top effects like windows going up in flames, so stuff like glowing window borders should be no problem at all.
By now compiz seems mostly unused, but many effects are also available in kwin. For instance
system settings -> desktop behavior -> desktop effects -> dim inactive
Kinda the opposite of outlines, where it just dims everything else instead of highlighting one, but maybe it works for you?
Also it makes it hard to work with multiple windows, because some of them are dimmed then.