I personally feel that if you look at vaping from the "what is going on in there" standpoint, you can answer most of the questions you have. For starters, you can only apply a certain amount of wattage before you start burning something. Wattage is basically a measure, for our purposes, of how much heat is going to be created at the coil. Picture a pot of boiling water on a stove. If you apply more heat, it will boil faster, but the volume of steam created will depend entirely on the amount of water that is available to boil. If you want more vapor, you should find a way to provide more liquid to be vaporized by the coil. A larger diameter coil, will hold more wick, and thus make more liquid available to vaporize. Multiple coils should also provide more vapor, as it is like having 2 pots of water on separate burners. This is just my opinion, from my observations of 4 years of vaping, I am not trying to start an argument with anyone.