Wire gage: mostly preference, yes. But 10 wraps of thick wire is going to be a lower resistance than 10 wraps of thinner wire because 'the pipes that the water flows through' are bigger. So, if I want low resistance but lots of surface area I'll want thicker wire. It's a balancing act.

Rebuildable dripping atomizers (RDA) are pretty easy to build on and usually have lots of air flow. The mutation x is easy to build on. I have a v1 and I'm thinking of getting a v3 soon. I also like my freakshow mini (I'm sure the standard size is good too) but there's a little more technique to building it properly and most of my builds are similar, where as in my mutation I can do crazy big and hot coils.

Rebuildable tank atomizers (RTA) are wonderful if you don't want to re drip. I've only had the lemo drop (which is great) but ended up liking the wider airflow on drippers and the ability to switch flavors easily more. Its also nice to know that I can dry out my wick on a dripper and not have to worry about it leaking in my pocket like a bad build in a RTA would. That said, I've heard the subtank is fantastic.

Mods: I was recently shopping for a replacement for my ticking time bomb (Istick 50w) and nearly got the smok m80. Be aware that the temp control on it is not the same as standard temp control and doesn't seem to work as well. If you want temp control look at the ipv4. I nearly got that too, but after getting burned with the Istick I'm worried about buying something that doesn't have a solid history yet, so I presently ordered an sigelei 150w.

So, if you want temp control take a risk on the ipv4; if you want a well priced 50w(?) mod get the m80. You probably won't have an appreciation for temp control till you've spent some time building and by then more temp control devices should be out so...m80 sounds logical to me.