Work-around
In my case I have to max-out the iGPU frequency with:
sudo intel_gpu_frequency --max
Root cause
Even when games use the dGPU, the cursor still uses the iGPU.
The iGPU still thinks that the desktop is idle when using the dGPU, so the iGPU stays at a low frequency and the cursor animation is choppy.
As result, when you move the cursor on a game the camera is also choppy.