Here is what I have found when using an rDNA40 & Subtank with nickel and temperature control.

For some reason temp control can be finicky with the Subtank. I suspect all the different pins/metal the electricity has to flow through before it actually reaches the nickel and tell the chip, "oh hey, this is nickel not kanthal"!

I usually fire my rDNA once without an atomizer so it know nothing is connected. I then connect the Subtank and turn the wattage down to 8-10W and fire while inhaling. You won't get much at first, but you're trying to get it to register temp control right away before the coil gets too hot and you get inaccurate readings. After the first "test fire" I'll turn the power up to around 20W and temperature between 380°-440°. I get no dry hits and vapor production that would rival using a regular kanthal build. 80% of the time this technique works. When it does not, I remove the Subtank and allow it to cool back down to room temperature. Sucking through the drip tip with the atomizer disconnected can help it cool faster. I'll switch to my 528 Monster V2 (think modified Kayfun) and use that while I wait for my Subtank to cool off. I repeat the 8-10w test fire for the Subtank again once cool and it's usually good to go!

I don't like using Ni200 for an RDA. Just not my thing. If you're expecting your temp control device to act like a mech mod. Use a mech mod.

I will say that temp control works perfect every single time on my Monster V2 and other modified kayfuns. I prefer Ni200 in tanks period. Getting a dry hit and ruining your wick on a freshly built Kayfun is such a bummer. Not to mention the juice you loose! Temp control has eliminated this problem for me.

If you want some big clouds on your rDNA40 device. Keep in mind it fires all the way up to 9V! Use that extra voltage!