Its seems like all the new stuff has terrible airflow or dual coils. With my SI T3s I get a ton of vapor and flavor without having to draw for very long. With unitank I have to draw for three times as long. Also the dang things taste like they dididn't fully wash out the machining oil.
Yup, just like with flavor, airflow and vapor production are subjective. On the unitank you might try doing a primer puff to start getting the coil going then take your draw (kinda like smoking a cigar, or what you see most doing with a RBA).
It is generally recommended to rinse out new toppers with hot water before first use.
If your situation allows, I would try an Evod. To me the airflow is a little looser than a T3 and I get great vapor and flavor (using 50/50 mix, 1.8ohm heads at about 8.5 watts). Only problem for some is that they are only 1.6 ml, but carrying a couple spares is easy enough usually.
Vape On!
