I'll try to answer you questions this time hehe.
There are 2 models of 2 piece 'cartomizer' style e-cigs. They are the kr808d-1 and the Greencig E8/E9 model. They are compatible with each other and have the same thread size as the DSE901/RN4075. They will not work correctly on a 901 battery or passthrough though as they get their airflow from holes in the threading/connection and center post area. A 901 gets airflow through a small hole in the atomizer.
So no, there are no cartomizers for 510s, 801s, 901s etc. It's an entirely separate type of e-cig.
Benefits are, better throat hit and taste (at least on the kr808d-1 model) and as much, or more vapor than almost any other standard e-cig (probably on par with a 510 in this regard). Ease of use is a biggie as well. Just use em until they dry up and toss them or refill them if you like. kr808d-1s are very easy to refill. Check out the DPV9 thread I linked to previously to see Crashes reviews of the model, how to refill, etc. Do some more searching if you need more pics or vids.
Downside is that they cost more than a standard 3 piece if you just toss them after one use. If you refill, then this isn't much of an issue. The only other worry I read about is that the kr808d-1 cart filler material tends to burn. I haven't run into this much myself, and when I do, I just toss the cart (usually happens after several refills). Supposedly the Greencig carts don't burn and last longer, but they cost more.
That's just a quick overview though. Search and you should be able to find a lot of really good threads. IMO, they are far and away better than any other traditional 3 piece e-cig. I have yet to try them on a high volt mod, but they can't be beat at 3.7v!
