For competitive play, you need at least 240Hz. 120Hz is more for the average gamer and PC usage. Just connect a PC to your C9 and you'll notice that even scrolling in chrome and mouse movement is massively improved compared to 60Hz(you can try at 1440p if you don't have HDMI 2.1 GPU). The first time I tried a 144Hz monitor I was blown away. Same with 90/120Hz phones.
If I'm going to even play casually on a TV, I'd want a TV with VRR (way more important than 120Hz) and at least 90-100 Hz. It makes a lot of difference. And if I can't afford such a TV, I'd play on a 1440p 144Hz monitor (available from ₹25k).