My pet peeve is the default clipboard behavior, personally I hate when I select text and it overrides the previous content in the clipboard.

That's not the default in all Linux desktops I've seen.

There are two clipboards in X11. One is the middle-click-paste, selection clipboard that gets clobbered when you highlight something. But C-x, C-c, and C-v (in CUA applications) operate on a different clipboard altogether that doesn't exhibit this behavior.

And that is awesome feature that I miss a lot in other operating systems.

It's a wart of X11, which is obsolete and deprecated. Wayland has a single clipboard which behaves in mostly the standard way.

clipboard and selection buffer are separate, though I think there is a situation that co-mingles them.