I use KDE Neon on my laptop and I’d prefer to have KDE as a DE on this one too (if possible) but I don’t mind a non Ubuntu base. Basically I’d just like to be able to play games on it without much hassle but I know how to paste commands into the terminal if the need arises.
To Realy harness every single BOGOMIP, there is only one: gentoo with cpu specific compiler flags. Distcc helps.
For everything less it does not really matter. Use the one you feel good with.
And to be honest, gentoo is my daily driver. But on a threadripper… i would just put a fedora on it and call it a day