Seems that this old problem is here again. I updated my drivers from 510.73.05 to 515.48.07, and now I have low FPS again. Now I have a RTX 3070 and normally I have more than 100 fps (I use vertical sync) in high quality even when recording with OBS, and with the new driver version I have 20-25 fps (without OBS), or even less.
To be sure it was a problem with the driver version I reinstalled the 510 version and everything was fine again.