Your power profile in Windows, what is it set to? It should be on balanced by default, max performance doesn't let the CPU cores throttle down so will always be using high power even when idle which is not optimum.
Also leave task manager open and move the mouse around, can you see the CPU cores spike when each stutter happens? And then sort the view in the next tab by CPU usage and monitor which executable is polling during the spikes as the mouse is being moved around to narrow it down.
Also are you using an 8k mouse or something now? It's a bit pointless using super high refresh rates as these will use more CPU cycles if none of the above are issues. My 8k gaming mouse is on 1k for example and I barely notice any difference on a 240Hz monitor when gaming