I have the same issue as the OP with RBA's. He's getting a very wet and HOT vape from his nano. When I say HOT, I mean the temperature of the vapor droplets hitting the throat and lungs. Even at the lowest wattage setting.
With my Kayfun lite V2's I have this problem. The vape from a 0.5, 1.0, 2.1, 2.5, 2.8 coil all produces a way to hot vape for me. I choke everytime.
The problem is that the coil is exposed directly to your throat, and nothing to cool it down. It doesn't matter how little or how much airflow you give it, the coil is still exposed to the throat and generates big hot vapor droplets.
What I did was to make a special piece (out of 26g wire) that allows a "flavor wick" to be placed over the top part of the coil. Exactly like the Kanger protank single disposable
coils. By covering the top coil with a flavor wick, the hot coil is not exposed to your throat and a cooler hit.
I could not deal with the HOT wet vape, so I had to switch back to a ProTank 2 with single coil. The single coil has 2 top flavor wicks that cover the coil which gives a cool, velvet smooth vape. Just what I like.
OP, you may just have to ditch the RBA and go with a replaceable coil
tank that has a top flavor wick. I had to, and have $300 in RBA's just sitting.