I would like to know if the necromage perk works on enchanted weapons as well as spells. I know it increases the power of enchantments if you are a vampire. But what if you are not a vampire?

It only works on spells that directly affect your character. So typically, no, it does not work on weapon enchants.

Being a non-vampire will do nothing. It essentially turns Necromage into one of the most useless perks in the restoration tree.

Are you saying that a fireball spell used against a draugr is not more powerful when you have the necromage perk?

What? You're talking about the bonus against undead, correct? It would still work against undead enemies, but Necromage wouldn't give inherent bonuses to your weapon enchants. Necromage only applies bonuses against undead creatures and NPCs. Vampire PCs get bonuses to any enchants/potions/spells they cast on themselves because they are undead.

Look at it this way. Ask yourself who the spell is affecting, and who cast it.

Here's the breakdown, assuming you're a vampire:

Potion: You cast it, and you're affected. Thus, bonus.

Poison: You cast it, opponent is affected. If the opponent is undead, bonus. If not, nothing. If the opponent cast it, no bonus is applied.

Weapon enchants: You cast it, opponent is affected. If the opponent is undead, bonus. Etc.

There are weapon effects that DO apply bonuses to the player, which I'm fairly sure are boosted by Necromage, but that's because they are casted and affect the player.

This should also mean that weapon enchantments are 25% more effective against undead. Whether you're a vampire or not.

That's correct.

Exactly.

I see what you were asking now. I thought you were asking if Necromage increases damage against ALL enemies if the wielder is a vampire.

In short, yes, weapon enchants are stronger against undead enemies.