Just looking for answers and found this thread.
I have exactly the same problem, recently bought a new i7 Lenovo laptop with nvidia 1650 graphics to get a “better” experience than on my old Surface laptop.
But now although I get smooth framerate and hi res, my avatar and other riders are badly flickering! Sometimes very noticably, then almost nothing for a period of time and then flickering again - usually in the same places every lap.
So annoying I don’t really feel like using Zwift at the moment!