To be honest, I'm not really fond of any of these pairs.
Pandora and
PersephoneI think the Greek Mythology theme is too strong, and I don't particularly like either name.
Pandora doesn't have the nicest mythological connotation and I don't like
Persephone at all.
Persephone and
PriscillaWhen paired together,
Persephone and
Priscilla sound like the names of the wicked stepsisters in a fairy tale. Far too frilly, and I don't like that they share the same initial sounds.
Aurora and
AtlasDoesn't seem right to me. I don't like
Aurora very much, either.
Atlas and
AlbusNeither of these names are bad, but they look and sound too much alike to be used for twins (or even a sibset).
Atlas is intriguing; it looks and sounds nice, but I think mythology and geography before I think of it as a modern name. I do think
Albus is a nice name, but it makes me think of Dumbledore.
May I suggest
Alban as an alternative?
Atlas and
AchillesSame problem as
Pandora and
Persephone: too theme-y. I don't like
Achilles much either (the name or the character).