Sorry, not very helpful, but Nvidia officially didn’t support Windows 11 until Cuda 11.5.0 and you are using 11.1, so you could try upgrading to at least that version.
There are many settings in windows that can affect GPU usage, especially windows 10 and 11 where the GPU becomes a “standard” part of general desktop rendering activities. It’s possible that your general settings in windows vary between these two OS instances.
I think it is unlikely that a CUDA application that uses 15% of GPU in win 10 will use 100% of GPU in win 11 strictly for the CUDA work. Even if that were the case, the simple fact that we are comparing win 10 and win 11 means that the issue could be a microsoft issue.
For a WDDM GPU, microsoft owns the interface to it. NVIDIA has to request resources from the OS for CUDA, just like any other application that uses the WDDM GPU.
If you search on something like “DWM high GPU usage” you’ll find numerous writeups on the web discussing the issue and what to do about it, most of which have nothing to do with CUDA.
Taking a close look at your picture, it appears you are concerned about the usage on the “3D” graph. I’m fairly certain that has nothing to do with CUDA, and indeed might be due to different desktop rendering settings. AFAIK, there is a separate graph that you can enable to see CUDA usage of the GPU.
I can’t say categorically that there is nothing in CUDA that would be dependent on win 10 vs. 11, but in general I would expect most of the dependencies and “support” to be delivered by the driver, not the CUDA toolkit. The OP is running a 531.xx driver which is a CUDA 12.x driver.
Still, upgrading to latest is always a good idea when chasing issues (IMO).