This is the version of BG2 I played as a kid. The collector's edition doesn't really add a whole lot of new content to the game, but the new items you can buy from the specialty dealers in the back of AdventureMart are stupidly powerful. Most of them aren't useful to most character builds, but you can probably find at least one cool item there that'll make your charname super powerful. This might also be what added in the twister rune too? Not 100% sure tbh. I also heard somewhere that this edition is responsible for Drizzt's cameo.

Shield of Balduran makes all the beholder fights trivial and Vhailor's Helm shows you exactly why simulacrum is a bit OP for a fighter ability.