Not a gamer and not a tech person. Just a forum observer. If I type 'fps gaming' into the search bar I see some SOLVEd threads that resemble your nvidia dilemma.
Your dilemma, you said, was some steam games dragged in fps rate, and most did not. Maybe peeps are waiting for some trial and error and troubleshooting on your part since there seems to be so many variables to your problem.
I am sincere and not facetious: when I first joined, with roadbumps, it took me a while to realize the more investment I gave my problem, the more investment I got back.
What have you tried? (edit🙂 maybe the board can whittle it down---)