Same issue here, I am getting 15-17 FPS regardless of the in-game settings. VRAM usage is low and power draw is only about 70 watts in my case. However, GPU usage seems to be almost at max.
I contacted NVIDIA support through the support form for consumers describing the same issue, as well as Bethesda support.
I also maintain a Reddit post discussing this issue with current workarounds, which don’t seem to work unfortunately.