Just to try to clear up some of the generalized confusion:
Battery:ego or ego-t doesn't make much difference, as far as what you can use with it. I THINK all the ego-t batts have the 5-click on/off feature, if they're made by joye. Some, if not all, of the normal ego (non -t) batteries don't have this feature. However, this has nothing to do with what can be used with it.
Atty: ego-t atty is not meant to be used with a normal cart. Requires a tank cart. I've been told that the ego-t atty isn't good for dripping, but no direct experience there. ego xl or 510 atty, dripping should be no problem, although I haven't used an xl atty yet. Just different varieties of 510 atties. My ego does tend to leak a bit on occaision when I'm dripping, but not excessively. I just keep a tissue nearby, and wipe it off if it happens.
Cart/carto: Carts (cartridges) are used with an atty. t or normal cart depends on the atty, and they aren't meant to be interchangeable between the t and non-t. Carto's (cartomizers) are a combination of cartridge and atomizer. So if using a carto, no separate atty is needed. Also, carto's are definately NOT suitable for dripping, as they normally contain filler material. Bypassing the filler material is one of the main points of dripping. Only need a few drops instead of enough to saturate the filler material.
2 piece just means batt+carto. 3 piece is batt+atty+cart. But, the same battery could be used for either.
Mind you, this is all aimed at 510 threaded stuff in general, and ego's (which are 510 threaded) in particular. Just wanted to add this to clarify that when I say such will work with such, it's all talking about 510 stuff. Oh, and although all 510 stuff SHOULD work with an ego batt, not all ego stuff will work with a 510 batt.
2 other points. I have no experience with the 510-t, but have told there are lots of compatibility issues with those, so if you're using a 510-t, disregard most of the above. And, there are charger compatibility issues between normal 510 batts and ego batts, so not mixing chargers/batts is generally a good idea I'd say. That's not true in every case, but is generally a good rule of thumb when first getting started, I think.
Maximillian the Vaguely Disreputable