Help with calculating voltage using watts/ohms (batteries/coils)
Modern e-cigarettes are usually vaped at between 10 W and 200 W. From your description it sounds like your particular atomizer is designed for the lower end of this range.

So try it at 10W. If that's too cool for you, increase the power by a couple of watts, and try again. Repeat until satisfied. No need to over-complicate it. 

Pre-coiled atomizer heads have a limited lifespan anyway. They rarely last more than a few weeks with regular use. You should treat them as consumables, because that's what they are.