These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Nightmare Fuel: All of part 2 of "Our Unfamiliar Home", no exceptions.
And everything in part 3 of the same arc, at least before the duos meet back up with each other.
Tear Jerker: Oh so many, especially in the recreation of Equestria. Twilight and Jack watching a corrupted stallion die after helping them; Rainbow Dash having to deal with the horrible orphanage Scootaloo once lived in, and finding Scootaloo's ghost in the process; Applejack and Rarity being scared out of their wits and nearly having a Heroic BSOD by this timeline's Ponyville hospital...and that's just in one chapter.