I guess I'm still confused about subohm and what exactly that means. So I see with the Kanger subtank you need a battery over 30w, correct? I'm only 2 days into this so I'm totally green as far as what everything means.
Subohm is when your coil resistance is 1.0 ohm or lower. There is some debate if the vapor produced by subohm coils could have some health effects, and there are safety considerations for batteries used in mechanical mods when using subohm coils.
The Kanger Subtank coils come in 0.5 ohm and 1.2 ohm. Not all devices will fire a coil below 1.0 ohm. Last year the majority of VV/VW mods wouldn't fire below 1.0ohm, but most of the mods being released this year will fire down to 0.5 ohm and some even down to 0.2 ohm.
The wattage you use is personal preference. Kanger's wattage recommendations are 15-30W for the 0.5 ohm coil and 12-25W for the 1.2 ohm coil, but it's still a matter of preference. I don't like high wattage. I am perfectly happy vaping my 0.5 ohm coil at 13-14 watts.
Online Ohm's law calculators are great for looking at the relationship between coil resistance and wattage. Take a look at this calculator,
Ohm's law | Steam Engine | free vaping calculators. Fill in the resistance field with the coil resistance and the power field with the watts set of a mod, and it will show you the voltage applied.