Mechs are nothing more than battery holders with a mechanical closing circuit. "Features" can be, among many... materials, button style, appearance, build quality and battery size capabilities.
If you intend to use the lower resistance coil heads available for the Atlantis, all you need to do is a single simple Ohm's law calculation to insure you have adequate battery current output.
You know your resistance value - in this example lets say you're using a 0.5Ω coil head - and you know your peak battery charged voltage of 4.2v. Enter those two values into an on-line OL calculator and you arrive at a current (amperage) value of 8.4 amps. This is a 'minimum requirement'.
What this means is... you require a battery with a continuous current discharge (CCD) rate of 8.4 amps, or better. That may be, depending on brand and size, any of the common 18XXX series batteries.
If we use one brand / size as an example - say a "new version"
AW IMR 18490 (18500) battery - we see that it's CCD is 18 amps. As this battery provides over double the minimum requirement, you're good to go.
A good rule of thumb for the "new to mechs user" is to use a battery that has a CCD about 10% greater than your Ohm's law calculation indicates. So, if you had a build with a net resistance of 0.3Ω, again using 4.2v as our constant, you calculate a current requirement of 14 amps.
Our AW IMR 18490 would again be a good choice, as you have a 4 amp safety "headroom"... but an
AW IMR 18350 battery would not be acceptable, as your drain requirement exceeds it's CCD by 2 amps.
The other consideration is run time. We can use an 18490 in our above build, but how long can you vape with it? People balance run time with size. If size isn't an issue, why not use a 18650 battery, to obtain a longer run time?
So... it's a combination of variables. Aesthetics and what you want banging around in your pocket vs. available run time.
