Boge cartos are single coil, while dual
coils have two coils wired in parallel
As for the performance questions, I can get similar performance from a single vs dual coil carto and I find that some juices taste better in one or the other or I like the hit on one better than the other with a particular
juice. My regular
vaping arsenal involves a variety of both single and dual coil cartos. It's all a matter of personal preference, so if you're curious about them just give 'em a try

You can buy cartos singly from some vendors. Madvapes is a good source there since they carry a fairly wide variety of cartos and their prices are good