You made a very generic statement, that V-Sync conflicts with frame gen. This is not true as global statement. To be honest, you are the only one experiencing this issue. So you have another individual issue. And you should try to identify it, since it is very unlikely others do it for you.
If VSync off solves the issue for you but causes tearing try using the frame limit to lock FPS make sure you set it to multiple of your FG. Ex: If your Vsync is 60 and your FG is set to 2x, lock frames to 30FPS. That will keep frames below your monitors refresh rate when FG frames are added, and prevent tearing!
I have observed Your same problem. I will try to deactivate the Vsync vy Nvidia App Panel, and we’ll see.
Moreover, in the SU6 it seems that the Vsync will be available INTO MSFS2024 also for the frame generator: there will be a reason, if they have chosen to implement it, isn’t it?