There are all kinds of atomizers and cartomizers you can use with the eGO (whether or not it is a pass
through): 510 atomizer (regular or LR), 306 atomizer (regular or LR), mega eGO atomizer (along with the mega eGO cartridge) ... 510 cartomizer, CE2 cartomizer, and mega eGO cartomizer.
The difference between an atomizer and cartomizer is that a carto is an
integrated atomizer/cartridge: no dripping or frequent topping off or refilling of cartridges required. Prefilled cartomizers
never have to be filled with
e-liquid, although most of us do to save money. But they don't need to be refilled as often as cartridges. And most cartos more effectively deliver the juice to that atomizer portion than most cartridges.
An exception is the mega eGO atomizer and cartridge vs. the mega eGO cartomizer. The each hold over 2 ml of e-liquid, the mega eGO atty/carto is pretty effective in juice delivery and easy to refill, whereas the mega eGO cartomizer is more cumbersome to refill.
All that being said, I personally don't like cartomizers. I prefer to drip (e.g., using a drip tip) juice directly on the atomizer every few minutes. I find the flavor to be purer and the vapor and TH to be more intense.
I suggest that you try various atomizers and cartomizers to see what
you like best.