Hi, I experienced exactly what you describe, too. Especially when flying in VR. It took me months to find out, that lowering MSFS to low in the process priority (task manager) gets rid of the stuttering issues after the hardware upgrade.
Please don’t ask why setting the process priority to low helps, but in my case it solved all of my problems.
I‘m using Windows 11, latest Nvidia drivers (overlay disabled), HAGS off, gamemode in W11 off, ultra settings in MSFS, no FPS limit in NVCP or in game.
Hope it works for you, too!
In my case the priority was reset to high automatically for some reason while MSFS was running. That’s why I now use process lasso.