FWIW, I've used Fedora's KDE spin [1] and its very polished. That said, if I was still using linux on the desktop these days I'd go with OpenSUSE Tumbleweed[2]. With KDE my experience was that they made big improvements with every release, and tumbleweed was a nice way to get a stable-ish rolling release distribution that gets all the nice KDE updates without me having to wait another 6-8 months.
[1] https://spins.fedoraproject.org/en/kde/
[2] https://en.opensuse.org/Portal:Tumbleweed