Help - Slow performance - Am I doing something wrong?

Hi all!

Both "NHL Legacy" and "God of war 3" are running like crap on my gaming computer.
Like 5 to 15fps, with the audio really stuttering.

My gear : 
Ryzen 5 5600x
32gb
RTX 3070

Tried with default settings, and many optimizations that I saw on youtube/forums/reddit. The result is always the same.
CPU utilization is always 100% and GPU staying between 5 and 20%.

Hope someone can find out what's going on

Thanks!