Just broke out the old trusty CE5 to compare airflows. I just got the kanger subtank mini today, so I am trying it out as well. The airflow of the Subtank fully closed is about the same as the CE5. Even fully closed, a tiny bit of air comes between the airflow control ring on the subtank. I have a .5 ohm coil, and I lowered it to 15w (3.0V). Flavor wise, it's much better than the CE5. I'm using an old coil in the CE5, but the flavor is so dramatically different even at that low setting, that I doubt even with a new coil, the CE5 would perform better. I have a lemon bar cake flavor in the tank, and the lemon flavor is so pronounced in the subtank, it tickles my nose. On the CE5, it smells like lemon, but doesn't tickle. The one airhole setting on the kanger is what I call max for a mouth to lung inhale. It's not something I recommend for mouth to lung inhales, but it's still too tight for direct lung inhales. The two and full open settings are for direct to lung inhales.
... this is the first time I've tried to vape with the subtank fully closed.
I haven't tried the Nautilus tanks. I used a protank for a while and got disheartened with Aspire. I'm a firm kangertech fan now.

That's not to say Aspire makes good products or designs, it's just I haven't tried them lately... vape budgets.