A330's engine...

[qunow]

Why in the game, there are PW4152/PW4156 for player to  choose from for A310 while there are only a single "PW4000" for A330 for player to choose from while the A330 can also be matched with different PW4000 sub variants?

[freshmore]

Probably because the difference in fuel is either no data or no difference. In real life the sub-variants of the engines are mostly down to thrust ratings I would imagine. This matters in real life but in AWS is not important.

[NovemberCharlie]

Why in the game, there are PW4152/PW4156 for player to  choose from for A310 while there are only a single "PW4000" for A330 for player to choose from while the A330 can also be matched with different PW4000 sub variants?

Same goes for the 737NG.
The -800 is available with 24, 26 and 27k rating I believe

[Zombie Slayer]

A310 the engines were introduced at different times and do not come with an increased MTOW so they have their pexcise names. On the 737 all engine options are available from launch and the higher thrust engines bring an increas3d MTOW with them, so instead of the long string of letters and numbers that follows the CFM56-7B they are named by the respective increase in MTOW.