Summon will grab the mobs in the order the game populates them, never in the order that they appear in the area you are in or that you see standing in the same room.

Summon works with multiple keywords. So you can use 'elite dwarven'. Basically, however many keywords you know apply to the mob in question to get the one you want (If you're using numbers for any reason you only need to apply it once i.e. c summon 2.elite dwarven)

Mobs can save against summon just like any player, and you won't know the difference between you summoning the wrong mob from an unsummonable place, an unsummonable mob, a mob that does not exist currently, or just plain failing the saving throw or even screwing up the syntax for the mob.

Mobs cannot be summoned from another continent.

Empire has a cabal ability in the black sect that makes summon stronger so it's harder to save against, and there are a few edges that affect the spell/commune.