Typically, a lower resistance means you can run higher wattage. While resistance (measured in ohms) is definitely a factor in how much power it will take to get the best performance out of a coil, the physical size of the coil tends to be more important. In fact, Smok has several different coils available for the Big Baby Beast tank that are all 0.15 ohms, but they all run at different power levels. This is because the physical size of the coil in each coil head will be larger or smaller depending on the design.
The highest-powered sub-ohm vape tanks will be physically larger tanks, along with having more airflow and usually a larger eJuice capacity. The physical size is important because it provides enough room for the large coils to fit in the tank, more airflow is important to allow for bigger clouds, and a higher juice capacity is important because high-powered tanks go through more e juice than lower-powered vapes.
Each vape tank will be limited to a few coils that are intended for use in that specific tank. One tank often has at least two types of coils to choose from, usually offering a lower-powered coil and a higher-powered one. You will rarely (if ever) see a single tank with a super high wattage coil available alongside a super low wattage coil, because different tanks are designed for their respective purpose. You shouldn't buy the most powerful tank on the market if you want mellow vapor production that doesn't call attention to you, and you shouldn't buy a lower wattage tank if you want huge clouds.
When choosing a tank, keep your vape mod in mind. If you have a dual 18650 mod you can get pretty much anything you want, because you have plenty of headroom for wattage and battery life. If you have a smaller or lower wattage mod though, you want to find a tank that suits your available wattage and battery life. If your mod only goes up to 50 watts, don't buy a tank that's designed for 60 to 80 watts. If you buy a tank that forces you to max out your wattage in order for it to perform properly, you're going to experience significantly shorter battery life than something with a more modest wattage range.
If you don't have a mod that you can run a high wattage tank on but you want big clouds, check out our Sub Ohm / Temp Control Kits section!