Not using frame generation, just various kinds of upscaling. Happens when OBS is open on different monitor. If OBS is minimized then it stops happening. Obviously the drop in displayed FPS results in visible stuttering. How can I get Lossless Scaling to show the full 165 FPS.
As a workaround, if I drag OBS to the monitor that is plugged into Intel iGPU then Lossless Scaling works fine 165/165. If I drag OBS to a monitor that is plugged into Nvidia dGPU then Lossless Scaling framerate drops to more like 165/130. But it can fluctuate. Obviously I already tried disabling iGPU but it didn't help.