you asked for general info. im going to spill what i know about e36 models and options for the next 10 minutes. (i change how i word alot, so might be like 5 seconds of reading).
the e36 model line starts with the 91's and goes up to 98's. you can have any of the 3 series that is: 318, 323, 325, 328, 330, and M3.
you can also have any of the versions of thoes cars as follows. (thought im not sure about the 'ti'. i know it's availble up to 325.) the 'ti' is the hatchback model, much shoter in the rear but the rest of the car is pretty much full size.
next we have the 'is' model, this is the sports version of the above cars and includes certain performance accesories which im not sure of off hand.
'xi' is the all-wheel-drive line. im not sure if they offer this on e36's but it's a version of the 3 series nonetheless. (might be e46 only)
'iC' is the convertable version. thats self-explanitory.
'ci' is the coupe. now the tricky part. you can have a coupe iC but not a convertable ci.
so. time for engines. the M42 is the 1.8L engine for the 318's. M44 is yea 96-98 318 only and it's 1.9L. M50 is the first 2.5L for the e36's but it was only made 1 year (on the 92 325i's) it does not have vanos controll. the M50/TU is the exact same engine only with added single vanos controll and was in years 93-95. M52 is next up. the newest engine for the e36's. it's either 2.0L, 2.5L or 2.8L pending your model of vehicle. it's also single vanos and indluded the OBD-II hardware. it's production years are 96 - 00 as it was put in the early E46 323's and 328's. the S50 is the 95 M3 engine which is 3.0L and still ODB-I/single vanos. in 96 they changed to S52 which is 3.2L, double vanos and OBD-II.
OBD-I means it's the early version of On Board Diagnostics which is the engine software to conpute and change all the engine functions. the OBD-II is the same thing, only more limited in how you can change it, which is why you will see people listing "OBD-I conversion" as one of their mods.
so thats what knowledge i can offer on e36 facts and history. hope it helps.