Fastsync is NVidia's new "trick" for people who like to play on high FPS (no V-sync), but hate the tearing. It really does not help if your game plays below 60 FPS, which is what G-sync is used for.
Fastsync is software induced, versus G-sync which requires a special monitor with a chip built in.
So if you have a G-sync monitor there's no advantage to setting V-sync to "fast" instead of just "on"?
