Do they use regular sax fingerings?
I don't know about the akai, but the yamaha uses regular fingerings except for the very highest(palm keys) and lowest(C#, and Bb) notes which are slightly different. you don't really need these keys though, because the octave key can switch between 7 octaves(though this itself takes some getting used to). the other thing that's slightly different is the side keys, instead of having one for A# and one for side c, etc... you just have two keys: one that raises the note a half step, and one that raises it a whole step. this way, you can use the same key for A# and side C.
What are the most popular models? I've seen the Akai EWI-4000, but i hear there's a yamaha one, am i right?
yamaha makes the WX5.
Can they be used in a live setting well?
yes
Possible dumb question: Do i need a computer?
no. but you can use a computer as a midi sound module if you want. i do.
Do i need an external midi something-or-other? (i dont know much about midi)
Anything else i should know? I really want to get one.
the newest akai has its own sound module built in, so you can plug it right into an amp. i don't know how good it is, but if you used it, you'd probably be pretty limited in the sounds you could create. both the akai and wx5 have midi output. midi doesn't have any sound of its own. it's basically just messages that say what note to play, and how loud and other such performance related information. so yes, if you want to use midi(and in the case of the WX5 you have no choice) you do need an external sound module. but this is really where things get fun... you can decide if you want your instrument to control an analog synth, or a sampler, or an FM synth or whatever other kind of midi sound generating devices are out there. I use my computer, because there's really no limit to the different kinds of sounds i can create... i can make my own patches using samples, or use any of the thousands of software synths out there.