I can't say what is the best e-cigar (to do that I've had to have tried them all!). I've got a
Ruyan E-cigar which is a few years old (it's actually one of the earliest e-cig designs) and still works, and its fine for occasional use - for a change. The cartridges have a very nice cigar flavour, but I would say it would not be satisfactory as a primary
device. Vapour production and performance is nowhere near current models. I'll have a crack at the rest of the questions though.
The atomisers are not separate on an e-cigar - they are built into the body. When the atomiser goes, you have to replace the cigar body.
No you cannot get cartomisers for these models.
No, IMO they do not give more TH and vapour. They are all old designs (basically derived from the Ruyan I linked to above). While some of the copies seem to produce more vapour than the Ruyan, they'll be unlikely to produce the vapour production and throat hit of current types (eGo's, Riva's, Joye 510's etc.) The "fat battery" models like eGo/Tornado/Riva etc. are of similar proportions to the cigar but pack a lot more battery power.
I believe the Totally Wicked one is probably an RN4062 model. If you search the forum or Youtube for "RN4062" you will find some
reviews. But overall my opinion would be if you want something that looks like a cigar for occasional use, and don't mind the fact you'll need to buy a new body when the atomiser fails, go for it. But I'd also get something else as a primary
device that you're going to use all day.