It would depend on the smoker. A pack a day smoker like yours truly? 24 mg worked for me...but someone who smokes a pack every few days or so? I'd think 18 mg would do the trick.
IMHO, the most relevant information that would help someone trying to quit smoking by switching to the The Vape would be info on battery power and tanks. I've seen so many B&M's recommending a sub-ohm tank with a 150 watt Sigelei, it's laughable. A new vaper doesn't need that kind of work, that high an expense, and the hit's too intense for 90% of new vapers.
Recommend something with a MUCH lower price tag and a lot less power, Crappy! There's no reason a 30-40 watt device won't work for them, and an inexpensive, factory built BCC will give them the flavor and the vapor they're looking for. What battery comes to mind...the Coolfire IV, the EMOW, stuff like that. Variable voltage and/or wattage with a low price tag.
As for the tanks, I am so freaking sick of RTA commercials on YouTube, I haven't watched a vape video in a month! (And, for me, that's weird! I love vape porn!) But the whole RTA trip has gone too far - RTA's eclipse everything else on the market, and there are a LOT of other options on the market! Or, if you absolutely gotta recommend an RTA, recommend one that doesn't require a vacuum to work. The Prometey, the Nectar and (when it comes out in clone-form) the Haze Dripping RDA are what I'm talking about. RTAs that don't require a PhD in wicking, are easy to fill, and don't leak and dry-hit and can just generally ruin somebody's morning.
Or the Smoktech PBC, the Kanger Evod, the Nautilus. These are good, solid, non-rebuildable tanks (well, okay, you can rebuild the Nautilus, but you get the idea) that don't need a whole lotta falootin', Crappy. Screw a bottom coil into the base, fill that puppy up, and move on with your day! No leaking, no dry hits, and those coils last me weeks! And they're a buck!