I just kept lowering it til I felt that I went too low and it was negatively impacting my aim. I find myself playing at short (not CQC short) and medium ranges, so being able to turn and not do a 180 when I touch my mouse is pretty important, as is being able to actually turn when I hear someone behind me.
For reference, I mostly find myself playing Moira, Soldier, Junk, Ana and Zen, and Zarya if I’m forced to tank, so I don’t need crazy high sensitivity like Winston/Rein/Flanker mains, nor super low Sens like Widow mains.
My cm/360 is pretty much smack bang in the middle of what most of the pros use, I sit at 36.06cm/360, while most pros tend to float between 28-44cm/360.