IWD has many, many unique spells and items that just are not existent in BG2. Not to mention two new priest kits exclusive to IWD (for now) I can say these will cause a lot of problems if you try to import them. I haven't tried, though. An uneducated guess I admit, but I fear they will not be compatible.
Probably with the same problems. You should probably wait until the BG:EEs are updated to IWD:EE engine and mods that implement spells might help but only if they assign them the same ID.
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I guess worst case you could just rebuild them manually in IWD, shouldn't be too hard.
Btw, last i remember i could not transfer items to BGII from BG1..Is it still restricted?