To always make sure you're not getting vsync input lag, configure your games with an FPS cap. For ROE, you said it already forces a 120FPS cap, so you're set there.
For PUBG, configure it to either an FPS cap of 162FPS (that's 3FPS below your max refresh), or set it to be close to the average FPS you get in the game in order to avoid huge fluctuations in frame rate. Which of the two you pick is personal taste. I prefer capping my FPS close to the average FPS rather than capping to max Hz - 3. I feel motion blur and input lag is more consistent that way.
For games that don't have an in-game FPS limiter, check
https://pcgamingwiki.com to see if the game has a hidden FPS limiter that can be configured in one of the game's configuration files (.ini files and such.)
If a game just doesn't have an FPS limiter at all, you can use RTSS to set an FPS cap.
Finally, if a game has microstutter (aka "judder"), meaning high FPS but it looks jittery and not very smooth, using RTSS even if the game has an in-game limiter might fix that. (This is not related to g-sync. Some games have this kind of microstutter regardless of whether you have g-sync or not.)
Another thing you might try it to disable vsync. That is, make sure it's OFF in-game and also OFF in the nvidia panel. I have found that in some cases, using vsync ON will result in hitching/stutter in games that often suffer from FPS drops or freezes. So you can try that to see if that makes games smoother. It might add tearing though. In general, it varies from game to game. Some games I play with vsync ON (like Prey and CS:GO), some other games I play with vsync OFF (like Dragon Quest 11). As a general rule I do the following: Turn vsync OFF in the NVCP globally. When I play a game, if I get tearing, I set vsync to ON the profile for that game in the nvidia panel.
