Hey Chibisaurus
First off, please make sure you're schooled in Ohm's Law, Watt's Law, and you're comfortable using a multi-meter and an ohmmeter. The Smokeless Owl is a mechanical mod, meaning there's no built-in protection if you under-build your head on the RDA. You need to understand how to build to fit the characteristics of the battery you're using.
There's a wealth of information from the user
@Baditude, regarding all this good stuff. He has a number of blog articles which talk about a lot of the questions you have.
18650 describes the size of the battery. The "18" part has to do with the diameter of the battery; the "650" indicates its length.
Batteries will have what's called a CDR - Continuous Discharge Rating. Make note, some batteries may advertise a discharge rating, but it doesn't mean it's continuous.
I believe it's RTSVapes who is well-known for selling AUTHENTIC batteries (some batteries offered are re-wraps and may not be as advertised.) Even though the Smokeless Owl is only about $25, you shouldn't skimp on batteries - I have heard to stay away from anything with "Fire" in its name. I do use Efest batteries, but I treat their ratings as about 1/2 what's on the wrapper, and even then, only build to about 1/2-3/4 that capacity.
Get a GOOD quality charger - Xtar and Nitecore Intellichargers are better quality There's a third one - can't recall whose - that's also very good. Again, not a place to skimp.
Hopefully some other peeps will raise their voices for you.
(I'm also eyeballing the Owl, just haven't decided to pull the plug yet.)