As for nicotine levels, skip that high concentration stuff. You are a heavy smoker right? The average range for a full flavor cigarette is 17-22 ml/ml concentration. By buying that high concentration stuff you are actually increasing your nicotine addiction and putting yourself in severe risk for nicotine poisoning.
As for pricing, it depends on where you live and where you buy. I cant make any suggestions there except if you are new to vaping don't spend a shit tonne of cash. The secret the vape companies like Smok don't want you to know is that all of the units are made in the same three factories in china...even the ones that claim they are made in the USA/UK/Outer Ozzywandia. All the circuits and shit are interchangeable and compatible, dependent only on the machine thread used on the fittings. Just like microscopes, TVs and microchip processors and LED screens...
As for battery size, it depends on usage, coil type and tank style. I highly suggest you get a variable voltage/wattage type battery. Some times you want a big hit, other times you just want to sip away. Most, if not all of the vapes are 4.2 volt circuits, so all those milliamp hour ratings just indicate how often you need to recharge.
The real area I suggest you review is coil and wick combinations. I do not know why they sell top coil vapes. They are shit, wear out fast and are not rebuild-able. They also use longer wicks and are prone to leakage that will short out the control circuits in your battery. Bottom coil units are superior, the last longer, and use significantly less wicking material.
As for the FDA regs, I wouldn't sweat them too much. Its the FDA for Christ's sake. All you will see is a price increase and proper labelling. Right now, I personally support that completely . There are far too many f*cking morons in this country that are ruining a good thing for the rest of us. For instance, I challenge any of you to list every single ingredient in your juice. The only reason I can do it is because I drove down to Lincoln and harrased the maker of the juice I use. turns out they don't even have a real chemist on staff. I feel safe in betting that is the norm.
Like any new fad product lots of claims and promises are made and rarely are they backed up by valid facts. Case in point is the claim e-cigs are not tobacco. This is complete and utter bullshit. The cheapest and best source for nicotine is tobacco. Period. It is dangerous and toxic to synthesize, and is far too expensive to do so.
Truth be told, I'll predict right now that in a year or so it will be released that vapes and e-cigs are just as bad if not worse than more traditional tobacco products. In fact I feel confident in stating e-cigs are the worst of the lot and vapes are the least just because of the way the nicotine is delivered.
Another issue everyone ignores is the heating coils themselves. Guess what they are made from? If you use a brand that has nichrome coils, you are giving yourself a dose of chromium and nickle with every hit. Both metals are toxic. If you use a kanthanl stainless coil like I do, you are getting mildly radioactive and highly toxic cobalt in every hit, along with sulfur, aluminum, copper and a range of other metals.
Well enough of that ranting, I guess what I am trying to say is nothing is ever what it seems, and profiteers are always out to make a buck off their customers. In other words, the buyer should always beware.