I may be dead wrong but I believe you'll find your car has a chain.
The M20 inline six (used back in the 80's and early 90's) had a timing
belt. Not sure what other may have had belts back when but I'm pretty
sure the newer models are all chain.

The twin cam 24 valve engines are all chains. So basically after about '92
or so.

Pretty well none.

John Burn's site is pretty good.

http://www.unixnerd.demon.co.uk/bmw.html

Perhaps because they make a wider range of models - and the engines are
the heart of their appeal?

Chain.

Yes, that's correct.

What you are facing in your range of choices is the line between OBD I and
OBD II. What you really have is a 4 cylinder and a 6 cylinder. The 4 comes
as the M42 and M44, the 6 comes as the M50 and M52. There is also a car
called an M (for Motorsport), but that engine is the S50 or S52. In all of
these choices, the OBD I cars (before 1996) is the first listed, and the OBD
II cars (1996 and after) are the second listed.

You appear to be only interested in the M52. This motor can be had as the
323 or 328. The 323 has a 2.5L displacement, the 328 displaces 2.8L, and
both of these motors are essentially the same from a mechanical
perspective(a difference such as this can be accomplished by changing the
crank shaft and connecting rods).

There is not really a dizzying array of selections.

PS
OBD (On Board Diagnostics), I and II are the engine management schemes. OBD
II is the better choice, but it comes into play from the 1996 model year, so
your search strattles the line -- and hence the extra confusion. As you move
into the '99 and later models, the 325 reappears along with the 323, 328,
and the addition of the 330.

Shop for your price range, it's far easier than shopping for engines. As a
practical matter, most can't tell the diffference in the engines, especially
on the daily grind to the office and back.