A common theme in all three stories is the negative effect of allowing fantasy to overwhelm reality. The boy narrator in "Araby" allows himself to fall into a dreamworld of adoration of girl he barely knows while Emily creates the "spouse" she wants by poisoning her beloved and living with his corpse. Goodman Brown allows what might have been a dream to color the rest of his life in a bitter way that never acknowledges the reality that all people are made of both good and evil.
In terms of literary devices, "Araby" is told entirely from the subjective point of view of the boy narrator and reflects his interior life. It is the most realistic and most plausible of the three stories in that nothing of a fantastic nature happens outside of the boy's mind, and unlike the other two stories, it ends as the boy has a moment of epiphany, realizing with "anguish" that his dreams are all a vain illusion.
"Young Goodman Brown" is primarily told from the point of view of Goodman Brown, but the omniscient narrator intervenes at the end to explain to us the effects the Satanic service had on the rest of his life. This story veers more into the fantastic than "Araby," as it is never clear whether the Satanic service is real or a dream.
"A Rose for Emily" is told by a third-person narrator and keeps us removed from the protagonist. We never learn what is going on inside of Emily's head. We are forced to interpret through outside actions what she is thinking and perceiving. This story falls in between the other two in terms of fantastic elements: it is pushing beyond the realm of reality, for instance, to imagine the town would not explore the smell of decomposing flesh coming from Miss Emily's home.
All three stories use the literary device of symbolism. In "Araby," the color brown represents the drabness of Dublin (note that the girl the narrator adores wears brown) and the bazaar Araby represents the yearning for the exotic. Hawthorne uses symbolism in which snakes represent the devil and Faith's pink ribbons symbolize purity or false purity, depending on how one interprets the story. Hawthorne's story, however, is more allegorical than the other two.
Miss Emily and the Griersons in general symbolize the South clinging to a mythic picture of the glories of the old days, while Homer's corpse symbolizes the grotesqueness of living in the past rather than moving forward to new life.