You can't use a dual coil on a Protank 2, but you can on the Protank 3. My standard rig is a PT3 with version 1 of the Kangertech Airflow Control Valve (the base which replaces the Protank 3's original base). The "version 1" valve is what came on the original (v1) Aerotank, and is available from several online vaping hardware merchants.
I don't like the valve that comes with the Aerotank v2, "version 2" of the Airflow Control Valve. It's VERY stiff and hard to turn. The v1 valve is much easier. In fact, I was worried that the adjustment ring was too loose on the v1, and that it would lose my setting when I put it down and pick it up several times, but it doesn't. It works very well for me.
I have an Aerotank v2, but I don't use it because I don't like the squared-off shape of the top of the tank. The Protank 3 has the nice curve down from the drip tip, which I find much more comfortable.
The range provided by the v1 airflow valve is wider than the v2 as well. You can set it wide open for a VERY airy draw - more airy than the v2 valve set wide open - and it's infinitely adjustable all the way down to a completely closed airflow. The v1 valve's range is 3.7 turns from wide open to fully closed. I keep mine set to one full turn down from wide open, which gives me a nice, fairly open draw with the 1.5Ω v2 (enclosed wick) dual coils.
(P.S. - Also, the v2 airflow control valve whistles when I use it, and it does it at almost every setting. Very annoying. I have yet to hear a whistle from the v1.)