I honestly don't know how much research has been put into TC by us, so this may have been mentioned a hundred times in old threads about DNA40 devices, but I thought I'd share my experience after a day of tinkering with TC.
This is with a single coil on an RDA...
Once I have the resistance set with the coil wicked and juiced I will perform a test fire of the device. Similar to when we do the water test of saturating the wick with water and firing it with TC set some level above 212 and watch where the temp hovers (right around 212), I fire it and watch where it hovers. If it's not reaching my set temp (Say, 420F for example) and it's hovering at something like 380F, I will change the temp to just above the hovering temp. This hasn't effected the vape quality, only the amount of temperature variant the device sees once the wick starts to run dry. If I were to set it to 450, and it typically hovers at 380 with no airflow, it has to see a 70 degree change in temp from where it's vaporizing the liquid, which I've found can produce a bit of a foul taste. By making that variant something a bit less drastic, like 10-20 degrees, it ramps off a lot quicker. Even though the wick will never run completely dry, I don't get any kind of foul taste.
I've found that altering the Joules setting will determine the difference between warmer and cooler vape temps more so than altering the temp setting.
This is what's working for me anyway, YMMV...
Now, I'm running a 70/30 PG/VG juice right now, so the vaporizing temp will be lower than a higher VG blend. I think 100% VG has a boiling point of 550'ish, so we should be able to find a "hovering temp" for any juice with the provided settings.
Also, I personally have not done the water test to check the accuracy of my TC. Not sure you need to if your temp is hovering at something less than the set value and you're making good vapor.