In CSGO and Valorant you can generally play with a lot lower sens than this game because there isnt as much movement or that many flanking routes so people who told you to play with lower sens is probably from a different game.
I think most players hover around 2.00 (1600DPI) or 4.00 (800DPI) 8.00 (400DPI)
On these senses you can play pretty much every character because your turn rate wont be too slow
But you also wont have jittery aim I find turning it down any lower gate keeps me from playing tracer or genji as I cant 180 fast enough, but turning it up is fine I just dont for consistency the higher the sens the less consistent you will be as there is more room for error, and because ive gotten used to it, but a lot of players have theres up by .25 or .50 so rather than 2.00 , 225 or 2.50 it is all prefrence though.
If you make slight changes you can adjust in a few days or weeks but major changes like going from 1.25 to 2.50 doubling your sens can take months to adjust but just make sure to keep it the same untill you get used to it.
If you dont want to do that I would just up it by 0.10 every day.
This isnt a great way to tell but after using your sens for a while youll know if its too high if you constantly overshoot (Aiming too far away going past them) and youll know its too low if you constantly undershoot (When flicking you dont aim far enough)
If you use a sensitivity higher thats higher than 3200 edpi I would probably change your dpi to 800 or 1600 having a high sens with low dpi makes your aim jittery amoung other issues.