How do you know GSync is on? I have vsync off, it says it can introduce input lag and it feels weird with it on, though I turned it on in the game options, not sure if it's different in NCP.
For G-sync the optimal settings are as follows
Nvidia Control Panel:
G-sync on
V-sync on
In game:
V-sync off
There is an indicator in the NV control panel you can turn on for G-sync.
Also its advised to cap your frame rate with Control panel or Afterburner to a few frames under your monitor refresh rate
Very much this, was just about to post the same thing