If you suspect stability issues due to newish hardware, downgrading is very rarely the way to go (unless the bug was introduced by a recent update).
Bugs get reported and fixed so you want to be doing the opposite, running a newer version of KDE and the kernel.
Have you enabled kde backports? If you're going to wipe the computer anyway, maybe give Tumbleweed a shot? It's running the latest everything while still being quite stable.