Basically it is this:

Base model 850: No name plate other than "850". Came with a five speed and zero options, a suede interior, ac, power locks and 15" wheels and a 168 hp engine. I owned one of these, a very reliable and one nice car.

GLT--Gran Luxury Touring: Name plate "GLT". Came with an automatic, but you had the choice of picking options such as leather seating, tracs, upgraded stereo, etc. Some years, 98 & newer, I believe they came with a light pressure turbo 190 hp.

T-5 and Turbo: Same name plates "T-5" and "Turbo", same model just different year, were simply a "GLT package" with a turbo charged engine- 222hp.

Platinum edition: I am not sure, but I believe it was the model in between the Turbo and the R. It had the 222 hp engine and Pearl white paint.

T5-R & R: Same nameplates "T5-R, Turbo 5-cyl-Racing" & "R, Racing" were the top of the line models and had no options, because they were given everything--17" wheels, alcantra leather seats, rear deck spoiler, sport suspension, wood grain dash, special front air dam and the better chip. Their engines were the same as Turbo and T-5 engines with a different chip capable of producing 240 hp for a duration of 10 seconds.

Hope this helps