DV has great prices for the PT coil heads. Also, if they are out of the PT specific col, check the eVod/protank coil head. They are the same exact coil. Kanger no longer makes the shorter stem coil head and now uses the same one for all there tanks. So if it says they are out, they might not be. That's what I did the last time I purchased them. Yep, same coil.
Far as which ohm you should get, the lower the ohms the hotter the coil, the more watts you burn given the same voltage value. I'm liking coils at 1.5-1.8 ohms. But then again, like 2.5 ohm coils too. Just turn up the voltage then. It all depends on your device. If you have a 4.2 volt device that is not adjustable then with a 1.5 ohm coil you are burning 11.76 watts, 1.8 ohms yields 9.8 watts 2.5 ohms yields 7.05 watts. 10+ watts tend to lead to a burnt taste and warmer vape, lower wattage vape is cooler. Whip out ohms law to determine what is best for your device. If you have VV and or VW mod, then its no big deal, just dial it in.
Ohm's Law.
where:
P = power in
watts
R = resistance in ohms
V =
voltage across the resistor
I = current through the resistor in
amps