Steam vr has interleaved reprojection which is doubling frames if it falls from 144fps down to 72fps… and then steam vr has asynchronous reprojection which kicks in between 143fps and 73fps, the effect is more subtle than interleaved reprojection.
Back in the day we could enable or disable each one, I remember I had asynchronous enabled and I disabled interleaved with the vive and then vive pro, some time ago valve removed these options and now it’s automatic.
Then valve added the motion smoothing which I have turned off since vive, and now with index I keep it turned off too.
Asynchronous reprojection is enough, if you have only occasional dips below 144fps then you dont need motion smoothing enabled.
Some people falsely believe if the framerate dips below 144fps it starts doubling frames using interleaved reprojection.
Interleaved could induce nausea, but asynchronous you wont even notice it much.