If the 0.15 ohm coil is a nickel coil, it should only be used in Temp Control. Nickel and Titanium coils can only be used in TC modes, but Stainless Steel can work in both, so I would see if your tank has SS coil options. SS will run in power mode so you don't need a TC mod, and will give a lot better flavor than Ni/Ti coils will, and they'll last longer too.
The problem with Nickel is after a certain temperature, the wire will start releasing Nickel Dioxide, which is dangerous to your health, but TC mods limit how high you can set the Temp to avoid this issue. When trying to Dry Pulse Nickel in Power Mode, you can actually see the wire melt from achieving too high a Temp, which is what makes it dangerous (you don't want to inhale molten nickel).
DO NOT continue using the Nickel coil without a TC mod.
The reason the mod wasn't recognizing the atomizer is because the mod couldn't properly read the TCR (Temperature Coefficient of Resistance) because Nickels resistance changes under load. The easier draw and bigger clouds is because the coil was a lower ohm rating (loosely stated, lower ohm coils produce bigger clouds). The better flavor is attributed to the TC nature of the wire. Temp Control will produce better flavor by regulating the Temp of the coil, preventing it from going over a set Temp, as juices will taste differently at different temperatures.
I hope that answers most of your concerns, I would recommend getting some regular Kanthal coil heads, or SS coils if they're available for that tank, and see if they come in a lower ohm rating. Most companies will make .25 / .50 / 1.0 / 1.5 ohm coils for their tanks, so hopefully you can find ones more suited to your needs.
