Fenris said:
I would suppose that the most powerful enchantment would mask any weaker enchantments.
If you take a look at the Staff of Power and the Staff of the Woodlands, their aura is "Strong Varied".
But the Cloak of Arachnida is "Faint Conjuration and Transmutation".
Likewise a couple of the Figurines of Wondrous Power - two schools listed at the same strength.
So I'd be inclined to say that a +1 Ghost Touch weapon would radiate "Moderate Conjuration and Evocation" - even though the Evocation, by itself, would only be Faint.
Multiple Evocation auras would not "stack" - so a +3 Flaming sword would simply radiate Moderate Evocation, just like a +3 sword or a +1 Flaming sword.
As for the double weapon... a +1 weapon gains bonus hardness and hit points. If you have a +1/+1 double weapon, would you add the bonus points once to each end, or twice to the weapon as a whole?
If you'd consider the hardness etc of each end separately, I'd say two auras of Faint evocation; if you'd add both to the whole wapon, I'd say one aura
-Hyp.