@Wayne Suslansky
Sub-ohm tank is a generic term used to describe a tank that is capable of using coils with a resistance of less than one ohm. It will typically also have a large amount of adjustable airflow.
The reason for this is that low resistance coils are more suitable for higher wattage levels. However with a regulated device the resistance of the coil does not dictate the power level, you can run it at any wattage level you like. So even though a sub-ohm tank is designed for higher wattages, you can potentially dial down the airflow and run it at a lower wattage better suited to a high nicotine level.
However really high mass low resistance coils will need higher power levels to light up sufficiently.
Generally if you want to use a lowish power level and high nic juice then get a tank suited to this application.
If you want to use high power levels and blow big plumes then get a tank designed to do this.
Which tank are you thinking of buying?