More questions haha, what do you mean by Vision is the top coil the kanger is the bottom? Im really new to this and can't believe how far the electronic cig has come. Also the replacement head's....the thing that goes inside the tank, is that different for all tanks or universal? And what exactally is a cartomizer a atomizer clearomizer and glassomizer?
I'm sorry! I didn't see this until now.
Ok, so top coil clearomizers have the coil near the top, where you put your mouth. These generally produce a warmer vape. Although since the coil/wick is at the top, you have to turn them over/swirl the liquid around once the juice level gets low to make sure the wicks are staying wet.
Top coil:
Bottom coil clearos (evods, protanks, etc.) have the coil/wick assembly on the bottom of the tank. This can be a cooler vape, but gravity makes wicking a lot easier.
Bottom coil:
As for the replacement heads, they're all generally different unless you have a few tanks within the same brand. For example, Protank (1, 2, and mini I believe) and Evod heads are interchangeable. Because they're all made by Kanger. Vivi Nova, V-Fate, and probably a few others have interchangeable heads too because they're made by the same people.
A cartomizer is a cartridge you fill with eliquid and is filled with a polyfill material and an atomizer at the bottom.
Cartomizer:
A clearomizer is a (usually plastic) tank that holds the eliquid, with an atomizer in it, either in the top or bottom like I talked about before. Evods, Vivi Novas, etc. are clearos.
Glassomizers are clearomizers, but with glass/Pyrex tank, instead of plastic. These are good for eliquid flavors that do not react well with plastic (cinnamon, citrus, etc.)
There are also cartomizer tanks, which is...a mutant

It's a tank like a clearomizer or glassomizer, but instead of an atomizer, it has a cartomizer in the middle of it. The cartomizer has one or more holes punched in it, so as you vape, liquid from the tank flows into the cartomizer and keeps it wet. You can generally hold a lot of liquid in one tank this way.
Carto Tank:
Did I completely confuse you?