Hy, i'm running the game on Ryzen 3900x, M.2 SSD with 3400MB R/W, RTX 2080
On Ultra settings with Raytracing i get arround 30-40 fps but the CPU & GPU are not 100% utilized (CPU ~40%, GPU ~20%)
On Ultra settings without ray tracing i get the same 30-40 fps

on both options the FPS often drops to 13-15

the temperature on both the CPU and GPU is between 65~75 celsius

Please advice what might be the problem

PS: I installed the latest nvidia gameready drivers

I Instaled process lasso, did'nt find core affinity, only processor affinity, (i asume that's what you were referfing to), it says 0-23

Yes, SO all your threads are enabled for this game

You can adjust the core affinity from the task manager when the process is running. The core affinity is the same as the processor affinity as far as I know. Just right click the process and there is an option to change how many cores are being used. I had to do this for Neir Automata to stop crashes. Disabling ever other core helped. Though I have not needed to adjust the core affinity for for CP 2077. They should be all running by default.

Also, I was having the same issue of low FPS (around 15). I just set the resolution to 720 p as some one recommended that. The game played fine at that point. I upped it to 1080p and it still has good FPS. You might want to try that.

And Dont worry about your cpu usage, my r7 2700 4Gh on all cores have the same usage, but my gtx 1080 is almost 100% used. Maybe check nVidia control panel if your card is properly set in gaming setting. Check power setting and cuda cores setting