It ends up being rather simple. You set the temp you want to vaporize your ejuice at, if while vaping you see "temperature protected", then you hit your target, and the device regulates the wattage-voltage to maintain that set temp. So what's the wattage you need to get to your set temp! That's where you experiment, as each different build might need a different wattage. I've done this many times. You have to monitor your devices screen. In my example for my coils, I start at 35 watts, I see the temp protected message, I lower the wattage, in 5-10F degrees, until I don't see the message, now I know I'm a bit too low in wattage to reach my desired temp, so I bump up 10 degrees, this range for me is about 25-35 watts on most of my titanium builds. Now the proof, temp set to say 470f, at 25 watts, vape a few times, then on my DNA200, Max the wattage at 200, same temp, same exact vape! Done the same thing on my VTC Mini. This is what temperature protection does, and it all makes sense. Now power, Kanthal vaping is all wattage-power based, you just have to retrain the brain for TC.
Read the linked thread I posted above in the Evolv DNA200 site, it's all covered, if your curious.