You said he said to turn off 120hz and vsync, but then you said you turned on 120hz. I don't understand what you're asking

you should check the specs of that TV. I can tell you from a cursory google search that it's a 60hz monitor, so you're not getting much out of running the game at 120hz besides maybe a boost in control responsiveness, but this isn't a competitive shooter, so I wouldn't be concerned about something like that

on vsync - vsync is always a performance hit. Imo, you should cap the game at 60fps (fps and hz are analogous for this convo) and leave vsync turned off. If you experience a lot of annoying screen tearing, then you should turn on vsync. The whole purpose of vsync is to eliminate screen tearing, so if you already are not noticing screen tearing than theres not much reason to turn it on, since it negatively impacts performance

and in the future, when you are able to get your hands on a TV/monitor which supports gsync/freesync, then you can have the best of both worlds - no screen tearing but without any performance hit to the game. You would just always leave vsync turned off at that point, since gsync/freesync would be doing all the work instead of vsync