Turn on G-Sync in the NVidia control panel and you're done.
Things like in-game V-Sync only ever apply when you're hitting the max refresh rate and you should really have a limit set in RTSS anyway, so you can leave V-Sync on if you like or turn it off. Unless a game relies on it to not mess up, you'll be fine either way.
The only adjustments I like to make are when I want to use ULMB for older games like HL2. I set the monitor refresh rate to 120fps for that and set up game settings so it uses ULMB, as the motion clarity from that is much better. Make sure you play it at 120fps with ULMB on (you'll need V-Sync or borderless windowed to avoid tearing) and set the DSR to downscale from 4k. You can still max the settings and get no drops. You'll get to experience the bliss of a high framerate, fantastic image quality, and wonderful motion clarity (
read this for LCD motion blur comparisons and why I choose ULMB if I can maintain a locked max fps).