Regarding the occult question.
One movie deals with it as good/evil, with limited abilities by humans to invoke. The other deals with it as good and evil coming from the same place, with no recognition of the difference. The choice as to whether magic is good or evil depends on the intentions of the sorcerer at the moment the magic is invoked.
Potter invokes magic with no observance of a God. "Magic" - to call what happens in both movies the same while comparing the differences, in Potter is invoking the powers of the unseen which can be, and are regularly, dark forces. Tho Potter has a pretense that he is a good guy, his magic stems from the same place as the dark magic. This is then a defacto admission that his magic is also dark, and he is therefore inherently evil.
In Narnia, only two beings are actually capable of Magic. Others may have some gift, but the gifts do what Aslan perscribes, such as Lucy's potion. Lucy is incapable of any Magic that does not involve the potion. Narnia invokes "magic" based on the word of Aslan (God) and the Ice Queen. The Ice Queen knows the "deep magic" because she was a witch before Narnia was created, but she does not know the deepest secrets of God, and therefore thinks she can kill God and in doing so become God. In Narnia, the magic is performed by characters that are clearly supernatural, not the humans, nor even the animals.
In later books, you will be introduced to Tash, who is the God of Calorman. Tash is another evil god, but short of appearing, I dont recall him performing magic. The last book has characters pretending to speak for God and perform magic, and then having to face the Gods they pretended to speak for.
Where does the magic the Ice Queen evokes come from?
He comes back to this point over and over, in many of the books, but probably the best illustration of this is in The Silver Chair, when Eustace and Jill are trying to hide from the school bullies, and decide they should try to get back to Narnia to escape. Eustace tells Jill you can only get there by magic, and Jill asks, "Do you mean drawing circles on the ground and incantations, and things like that?" and Eustace replies, "No -- and I don't think he'd like that." They make what amounts to a prayer, but before they can finish it events catapult them into Narnia - so their prayer was answered before it was made. Lewis has a lot to say in his more serious books about the problem of temporal prayer to an eternal God. As Eustace says to Jill in a later book, "It's the usual muddle about times, Pole."