There are 3 current "versions" of the G750 at the moment each with several different configs:
the 2 letter suffix identifies the GPU:
Jw = 765m
JX = 770m
JH = 780m also the case for the JH is different with larger heatsinks and bigger exhaust vents
next a dash then a set characters that id the specific config, as far as i can tell there is no rhyme or reason as to these. They are region specific presumably for keyboard layout. Ram amount, BluRay/DVD, internal drive type and size and screen type 2D/3D can all vary within a model: eg.
G750JX-T4099H is a UK variant has 8GB of Ram and 2x500GB HDD's
G750JX-T4199H is a UK variant has 8GB of Ram and 2x750GB HDD's
Hope this helps, and if you are considering buying a 750 I'd say you've come to the right place to find out about them.
