- City alignments based on AD&D.

Are Mages chaotic?

Chaotic good is someone who believes that good must triumph at any cost. That's how they start showering affection, doing good, and bringing benefits... :D

Well, not exactly... It's just someone who doesn't accept discipline, order, and authority as such.
In this case, I see the Rampart race as the most suitable for this role.
Something like this: a fantastic, good, and white unicorn saves a group of beautiful girls from an evil vampire... "Stay with us in our city as a professional vampire hunter, dear, we will feed you and brush your mane and tail!" - the grateful girls say. "No way, I'm going to swim in the moonlight!" - replies the good, but chaotic unicorn and flies away... across the wheat fields. :D

Is Sandro neutral evil?

In principle, considering that almost all necromancers in HoMM3 are depicted as, at best, half-corpses, it's doubtful that they have any emotions... Let's just say: they are too undead for chaos, and for order... let's just say, the idea of order and strict law doesn't occur to the dead, because they have no inclination towards lawlessness...