Well, some of the "heat" issues and other things are partially determined by what type of a tank you plan on using. My particular tank is designed for blowing clouds. I can, and sometimes do, take small mouth to lung hits but I have to turn the wattage down and take very quick puffs. But yes, up around 60W the vape can start to get warm. When I am running that high, I take direct lung hits and suck the vapor as fast as I can into my lungs in order to keep the vapor from being too hot. Generally speaking, the faster you can get the air moving past your coils when you are inhaling then the cooler the vapor will be. I am currently using 10mg and sometimes 12mg nicotine, which is pretty darn high for that much power but I was a heavy smoker for many years. I mostly use 10mg liquid and am going to be lowering it soon.
Concerning the IPV D2, I already seen pre production videos on the device and it is one sweet looking device. It is almost exactly the same as the mini 2 but with temperature control. Even though temperature control is rather new and manufacturers have lots of bugs to work out, I like it.
Yes, temperature control is definitely worth a go for sure. In the future most mods will likely be temperature controlled anyway. No, you do not have to use 3MG nicotine, because like I said, I am using 12MG on 55W at times and it hasn't killed me yet..... It all depends up on the person and how much nicotine your body can handle and how much you desire. However, I definitely would not go very high with the nicotine at higher power because you can easily get way too much into your body. Lots of folks use 6MG when they are sub ohming and others use slightly more or slightly less.