So let's see if I have this right...
The complete idiot's (pick me! pick me!) answer would be that dual coils should only be used with a large battery. It would work, but would kill a small battery rather quickly.
The difference between bottom and horizontal coils is basically only where it sits in the cartridge.
If I am looking for additional parts for the SmokeNV system that I currently have I should be considering Volt, Bloog or Halo batteries and cartomizers (unfortunately, I have only been able to find one source for Bloog in Canada and none for the others).
Have I got this all correct?
Yup. Pretty much nailed it.