middle click pasting is kind of a funky holdover from some software stuff, there's usually options to handle it but i have to confess i'm not that well versed in mint and thereabouts

as for customization, certain other environments (xfce) are kind of comedically customizable, to the point that the window border decorations and thereabouts are configured via Literal ASCII Art which can be anywhere from expressive to. horrifying

This is the theme we're currently using for our desktop in that front; tragically it's really hard to find good themes without making them for yourself because there's like one site that has a variant for like every window manager and desktop theming system under the sun that purports to be a hub for hosting said themes, and they all have the same completely unusable interface for scrolling through what end up being the most uninteresting themes known to man anyways :(