O.k., one at a time here.
Yes, all the ePowers use one battery at a time. Vape one while the other is recharging.
In my experience, clearomizers last longer. One reason is that, with a lot of clearomizers, you can clean them far easier, and with better results, than with cartomizers. I have clearomizers on their 4th and 5th weeks after being cleaned 3 or 4 times. Cartomizers generally last a week or two when not used in a tank. In a tank, they last longer because they are kept continuously wet.
When you use a tank, you don't replace the tank, you replace the cartomizer that fits inside it. You can get cartomizers with the hole(s) already punched into them, or you can get regular cartomizers and punch your own holes in them. The "pre-punched" cartomizers cost about twice the regular cartomizer price. The thing is, tanks that use cartomizers are not disposable. Some have replacement parts, like o-rings that seal the caps on the tubes, but the only disposable part is the cartomizer that fits inside.
Some clearomizers use their own mouthpieces, e.g. the Vision Giant clearomizer. Usually, it's the very large clearomizers that have their own mouthpieces because they are too big around for a normal 510 drip tip to fit on them. Most smaller clearomizers, the ones that are about the size of a regular cartomizer, can use a normal 510 drip tip (except G4s).
A conventional cartomizer contains an coil and some type of fiber filling, usually polyester, to absorb and hold the juice. If you let that filling get too dry, you risk having it burn or scorch. That ruins the flavor, and the cartomizer. When used in a tank, the carto is kept continually wet, so that doesn't come up. When you are starting out, you need to be careful and "top off" your carto frequently by dripping some drops into it until you learn the signs of a cartomizer that is in danger of running dry. When it runs dry and scorches the filler material, you will know it. Prepare to burn a carto or two until you learn the signs of a carto that needs to be topped off. (taste change, weaker vapor)
A clearomizer is like a cartomizer, except that there is no fiber filling. The juice is held in a chamber and fed to the coil by means of a wick. The outer shell is generally clear or semi-transparent, hence the name. Because the juice must be fed through a wick, they are sensitive to the thickness of the juice. Thicker juice doesn't wick as well as thinner juice and the vaper is more likely to get "dry hits". Most of them have the coil near the top (CE2) and the juice has to wick all the way up, or the carto must be tilted to get the juice to the coil. Some (CE3, G4) have the coil at the bottom and are better for thick juice. Also, the ones with the top coil usually have a silicone or rubber plug over the ceramic cup that contains the coil. This causes a burnt, plastic taste when new and most people perform some tweaks and minor surgery on the plastic plug, or discard it entirely. Doing this, however, introduces a risk of flooding or gurgling or leaking or getting raw juice in your mouth. When clearomizers are working well, they provide a cleaner flavor due to nothing contacting the coil except the juice.
There is no difference between the accessories you would get for an 18650 or 14650 battery powered PV. Both batteries are 510 threaded and both provide 3.7 volts. Some accessories are specifically designed for eGos. Those might require a $4 510/eGo adapter. But in terms of ohms, or resistance, there is no difference.
In a cheap e-cig, the piece that fits on the battery is often referred to as a "cartridge". It is technically a cartomizer, since it contains the coil (atomizer) as well as the juice in a one-piece assembly. Cartomizer =
cartridge + at
omizer
An atomizer is a one piece assembly that contains only the coil and relies on a separate piece (a cartridge or in the case of some eGos, a "tank") to hold and deliver juice to the coil. Don't be confused between the proper definition of "cartridge" and the way that cheap e-cig makers use the word. Their "cartridges" are actually cartomizers, they just call them cartridges so as not to scare new vapers.
If you don't have a PV that uses a separate cartridge or "tank" to deliver juice to the atomizer, the best use of an atomizer is for direct dripping. Instead of a cartridge delivering juice to the atomizer, you do it manually, drop by drop, through the drip tip that attaches to the mouth end of the atomizer.
A tank is easy to fill and clean. There are two types. One uses a cartomizer with a hole in it. The cartomizer slides into the tank, sticks out of both ends of the tank, and uses juice in the tank to keep its filler material wet. The other type contains it's own coil and wicks totally enclosed inside the tank, similar to a CE2 clearomizer. Good cartomizer type tanks include the J-Tank and the Mom & Pops tanks. The Smoketech DCT is not a very good tank, although it is cheap. The cartomizer can slide up and down and even come out enough to let the juice out and make a mess.
A good tank that doesn't need a separate punched cartomizer and that works on the same principle as a CE2 clearomizer is the Vision Stone 3. This is the one I use. It has replaceable innards, so it is not disposable. It tastes cleaner than any tank with a cartomizer because there is no filler. It's about the same price as a cheap Smoketech tank, and the guts are about $3. They also last a very long time, longer than the cartomizer you'd put in a tank. Plus, they look really, really, cool.
Gotvapes has the best pictures of the Vision Stone 3 Tank, but not necessarily the best price.
Look under the "tank" category on their website.
GotVapes.com, E-cigarette Supplies - Atomizers Cartomizers Mods Juice and more