Define not getting much more performance, you've shown the settings, but what FPS you got and are getting on each card. Most reviews suggest maybe 9% increase between the two cards.
What's your GPU utilisation in game(s)? Windows game bar has an easy-to-access utilisation widget.
Then it's not your CPU, or indeed the any other part of your system bottlenecking. The GPU is functioning as fast as it can. Sorry man.
I doubt there’s much of a real difference between those gpus with a 5900x. I wouldn’t entertain an eco mode on the cpu...