Solaufein comes with el-weirdo spells because ... (drumroll)
... when I first made his CRE, Near Infinity was the only option (TeamBG had some 'CRE Maker' or something but it was read-only) *and* it would crash or produce invalid CREs if you tried to cut/paste or otherwise modify spell lists. So if you look closely, you'll discover that Solaufein's spell selection is more or less a copy of Edwin's. I made an effort to include some of the more powerful spells (because people often complain that Imoen2 can't cut it unless you bring a library with you for her to read on entry) but all of that "summon X elemental" junk is left over from our favorite conjurer.
As for Pro-Magic Weapons, Improved Haste, etc. I don't want Solaufein to start with every advantage in the world. If he were a ToB-only character that would be OK. But in SoA you can't really/easily get a pro-magic weapons scroll before the underdark anyway. He comes replete with all of the spells your other party mages should have at that time, more or less (unless you did the underdark dead last and they're all 18th level masters).
I debated Spider Spawn, but I'm sure other Drow would expect him to be able to cast that particular spll as a wizard. It would "blow his cover" to refuse every time.