To add to this, G-sync doesn't work at all in Windowed Fullscreen. Probably the biggest issue I have and makes it hard to play since it's not smooth. I have the correct options set in Nvidia CP and also have it set to display when G-sync is active. I have to put it into Fullscreen mode, but then I can't run it in Ultrawide (2650x1440 is max setting there).
Edit: I don't know what changed, but I deleted my GameUserSettings.ini file and it recreated one - after that Gsync works in windowed fullscreen now.
Edit2: Rebooted and now it doesn't work again. Seems to be an issue with my LG 34GK950F. Gsync works fine in other games on it.