Most if not all spells use bg2 versions where applicable.
In bg1:ee, magical arrows and bolts use bg1 damage values:acid arrows do 2-12 extra damage, magical arrows do their enchantment bonus damage. In bg2:ee, magical arrows are nerfed:acid arrows do 1-3, magical arrows lack damage bonus.
Oh yeah I noticed that one when I was looking at the arrows in BG2... I was like why are they weaker? And I still don't know why they would've changed that. There's enough to learn as it is without the same things becoming different from one game to the next.
No, they nerfed archery. Which, in all honesty, was/is godly strong in the first game. Arcanists are still as flimsy the first couple of levels and absolute gods once they hit their stride.
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In bg1:ee, magical arrows and bolts use bg1 damage values:acid arrows do 2-12 extra damage, magical arrows do their enchantment bonus damage.
In bg2:ee, magical arrows are nerfed:acid arrows do 1-3, magical arrows lack damage bonus.
There are even mods that make it so the arrows in BG1 replicate their BG2 counterparts, I think this is an SCS component or a BG2Tweaks one.