Are you using motion smoothing? If not be sure to lock your framerate to 30fps in the headset to avoid stutters (you can do this in the nvidia control panel per game).
If you have 30fps and 90hz then each frame will be displayed for 3 refreshes, while not ideal it will at least appear consistent. If you have eg 35fps then some frames will display for 3 refreshes, some will display for 2 refreshes and it leads to a much more juddery experience.
If you have motion smoothing enabled then it will lock itself to 30fps (or 45fps, but that’s much harder to achieve in MSFS) as long as you have sufficient headroom, but it does involve some overhead and requires headroom to properly function too so you may need to turn down the resolution and/or some in game settings to get it working properly.
For me personally in MSFS I prefer to turn off motion smoothing (disabled in the OXR app) and lock to 30fps as it frees up some precious resources and the artefacting from 30fps reprojection is too extreme for me.
Make sure you are using either 457.30 or 461.92 as those drivers have the best results for me on my 3090, anything else is notably more juddery on my system.
It’s also worth noting that the latest update has some performance issues, while mine runs great 90% of the time (well, not great - I don’t consider 30fps in VR great lol, but great by MSFS standards) I occasionally run into some serious stutters and performance problems since sim update III.