Yes, you have to lock the coil resistance in for the TC function to work. If you don't, it will kick to wattage mode. The watts in TC mode are not real important over some minimum value. That's because the mod only uses the watts you set until the wire reaches the temp you set. Once it does, it backs off the power to hold it at temp without getting hotter. So long as you don't have long ramp up time (wait for the coil to get hot enough to make vapor) you have enough watts set. If you push the button and have to wait for vapor, you need more watts. But that's it, really; between those extremes it means nothing. You could set it for maximum, or in the middle of the range, and the vape would be the same.