Even though elves and half-elves have "Fey Ancestry", elves aren't fey. They're humanoids, which, to me, means they’re natives of the prime material plane. They were befriended by certain of the fey from early on in their history, which left an imprint on their culture and epigenetic expression, but they are not the same people.
For a literary distinction between a fey-touched human and a (non fey-touched) half-elf, I might look at Aragorn, son of Arathorn, versus Prince Imrahil of Dol Amroth. Legolas noticed Imrahil's elven ancestry at the meeting held in Aragorn's tent in Chapter 9 of Book 5 of the LotR, while many recognized Aragorn as the rightful king, possibly in part due to his divine lineage -- a sort of “divine right” made manifest through his descent from Melian the Maia.
Fey Ancestry grants resistance to charm which is a good start for a fey-touched humanoid, but to distinguish them from elves, I’d focus on other fey-like abilities like general magical resistance, ability to charm/put to sleep, ability to become invisible, etc. There are many, and you could take your pick I suppose.
ETA: Something like the sprite's Heart Sight would be a good trait for a fey-touched race, IMO.