Hit Windows key+G. It'll bring up the game bar on the bottom. Move your mouse over it so it doesn't go away and the game should load fine. Do the same during cutscenes and loading screens until they release a fix. That will allow you to use gsync.
I have the same issue. The splash screens when you fist load the game, any loading screen, and in-game cutscenes run a like 1 frame per second with gsync enabled. Turning gsync off in the Nvidia control panel seems to fix it. You can also hit Win + G to bring up the media bar and with that running while cutscenes are going on makes them run smooth. But it's annoying to keep having to pull that up every time a cutscene happens. So I just turn gsync off for this game until a patch resolves the issue.
Hit Windows key+G. It'll bring up the game bar on the bottom. Move your mouse over it so it doesn't go away and the game should load fine. Do the same during cutscenes and loading screens until they release a fix. That will allow you to use gsync.