thanks for thisI'm quoting you, but this post is a small PSA about this stuff:
Locking your monitor at a specific refresh rate and then inputting a lower refresh signal from a game, usually increases input lag.
If you play a game at 60hz output, the monitor should be at 60hz. Same with 120, 144, etc. It's generally less of an issue with newer monitors. As they normally just detect the input signal and automatically set that refresh on the monitor. But some monitors, such as Samsungs from 2 or 3 years ago, let you lock the monitor refresh in its menus.
Borderless full-screen also probably implies that a game's refresh can be independent from the monitor's.
Best way to tell is open your monitor menu and see what res and refresh it is reporting.
If you meant your desktop res is usually set to 120hz, it's likely the game switches your monitor to 60hz when it goes full-screen.
Gsync is recommended to be used in tandem with Vsync from the Nvidia control panel. Unless the specific game has a conflict and needs to use its own vsync code. Using vsync from the game or forced through driver Control panel removes the need to run a framerate cap just below the set refresh rate, along with gsync.
There should be no explicit need to run RTSS if the only reason is for a framerate cap. If that's all---you can cap framerate in both Nvidia and AMD control panels. And have one less app running and hooking into your game.
Souls games are games which can be picky and may need to use their own vsync code on some systems.
Adaptive refresh methods may not work well with Souls games (not talking about VRR).
Likewise, anything which 'hooks' into them can exacerbate stutters and frame drops.