supra "wave"? well, if that is the only reason why you want a Supra, i strongly suggest that you get something else. I'm not trying to offend you but there are enough people who have Supras only because of the hype as is.
But if you are serious but getting an MKIV and not only because its the "cool" thing to do, ill be glad to answer your questions (although a simple search would have given you plenty of information)
first of all, TT vs. Single. haha just because there are two turbos has nothing to do with basically how much "air" they can move. as you will soon learn, the Single Turbos are all pretty much HUGE especially when coming from the integ crowd.... simply put, more air, more fuel, more horsepower. there are alot of advantages. too lazy right now to go into detail.
93-98? well, there is the obd1 vs. obd2 thing that we all know, making the older models slightly easier to mod. also, the front bumper is ever so slightly different and the turn signals on the 97-98s are clear. and the headlight housing color as well as the tail-lights are just a touch different. Besides that, there isnt much else that changed. couple different colors..
with a TT, basic mods would be an intake, downpipe, exhausts, bcc blah blah blah, basic stuff, not really much to BPU, some get a FMIC but its not a step that everyone takes..that should be enough.. and it shouldnt run you 3000 dollars either. and it will put you right at around 400. the TTMKIV responds extremely well to simple mods.
hope that helps some, but seriously, dont get a Supra just cuz of some stupid movie, if that's the case.