Personally, I dont vape high wattage box mods. I havent had use for more than 30w regulated. some times I float around 30w on my cloud chasing builds, but generally I build higher for lower watts, longer battery life, and a cooler vape.
28ga is great for begining - its not so thick that you need to do a million wraps to get your ohms up, then you need to crank the watts to get the coil to perform, but its not so thin that its difficult to work with. I wrap around 7/64 or 3/32 usually, wicked with Japanese Cotton until I find a good build for the atty, then jump to ReadyXWick as it lasts forever, gives a clean vape and is really low maintenance.
My current rotation of RDAs is: Cy-clone (fasttech K6), Veritas clone, Zenith Clone, and very occasionally I'll use the kayfun. My standard build is .4 (26ga) to .8 for dual coils or 1.2-1.6 for singles - it just depends on the atomizer. mostly I've been running mechanical mods, but I've been rebuilding for better than a year and highly recommend starting on a box mod as it will save you as you make your beginner mistakes.
