No, the 6000 series and higher use DDR4 RAM

But I think the 4790k would be faster than the 7600k in most games (except for very old single threaded games which run fine on both anyways)

4000 series can do AVX2 (same as the 7600k), so it has all the commonly required modern instructions

I’m getting 10~20 FPS regardless of graphic settings. I’ve also checked on my GPU and it maxes out at around 50% utilization so I’m guessing the processor is my limitation

Yep that’s a CPU bottleneck. 4790k will be a good improvement for sure. IDK if it’s worth $100 but maybe, considering any other upgrade would require buying RAM.

I’ve been thinking of switching from Kubuntu to Fedora KDE

I don’t like rolling releases, I’d rather have point releases (like Ubuntu or Fedora), but Ubuntu is really far behind on a lot of packages