Hi Johan
Such a loaded question. Dry hits usually mean you're not wicking your
juice quickly enough to keep up with whatever you're firing. What's your PG/VG level? What's your nic level? Are you running a darker, sweeter
juice? What's the wicking material for your coil? Do you have VV/VW for your rig? Do you have sufficient airflow?
I rebuild my kanger heads (formerly for EVOD
tanks, now for Protank2s) to about 1.8 ohms. I find that lets me cover a wide range of options. I usually run anywhere from 8.5-10W for those (9W is my typical "happy place") I have a couple of Nautilus tanks with 1.8 BVCs that I can run at higher power than the PT2s to get similar to slightly better results.
I've finally started playing with an RDA, and lower ohms/higher power seems to draw a little more flavor than from a tank. Again, so much more physics involved. So, for day-to-day, I stick with a pretty normal range. When I'm experimenting, I stretch boundaries.
So, long, rambling answer somewhat shorter - it's all kind of an experiment. What works for me doesn't necessarily mean you'll get the same results. Play with it a little bit and see what combinations work for you.