You can't adjust the voltage...and it isn't regulated. It follows battery voltage. So it starts off at 4.2 volts for a bit, but is pretty much in the 3.7/3.6 range for most of the use time, then drops rapidly from there.
So the only thing you can adjust is the ohms. The more ohms, the cooler the vape.
So 1.8 could be a bit hot. 2.8 a bit cool. 1.5 is too hot for me, but maybe not for you depending on what you screw onto it. See?
So try 2.0 ohms ish. Maybe have a 1.8 or a 2.3 around. You may even want the 2.3 with a fresh battery and then switch to a 2.0 after a bit.