[Man-of-the-Wold]

I might further note based on what I'm reading in HoME V, assuming JRRT more or less maintained this structure, was that the Nandor (except perhaps those that later entered Beleriand as the Laiquendi) were neither Eldar nor Avari. They were in the middle, orginally he had intrepreted them as being in origin of the Noldor and with the name Danas.

So, in this framework, which JRRT may have later retranslated, the Silvan Elves who were of Nandorin descent were not Eldar, and so the Elfin ancestors of Prince Imrahil would not have represented a union of Man and Eldar, such as the might three: Tuor-Idril, Beren-Luthien or Arwen-Aragorn.

The Nandor in this sense, however, were not Avari, and like the Eldarin Grey-Elves (Sindar) and Green-Elves (Laiquendi) they had a deep longing for the sea and to pass in the West, which eventually awoke, and that most if not all of these Silver-Elves did so by the time of, or shortly after, the Last Ship left from the Grey Havens, which was primarily for the transport of the Eldar, whereas the Elves of Lorien had long tended to set sail from the Bay of Belfalas.

Possibly, some Silvan Elves, who were Nandorin, never left Middle-Earth, and like the Avari, they stayed and faded, but in contrast to an earlier Topic of mine, that would have thus left no Eldar in Middle Earth after the early Fouth Age.

Also possible is that a large part of Thranduil's Realm was comprised of Avari who had eventually wandered eastward, and was not so much Nandorin. The people of Lorien were probably almost entirely Nandor or Eldar.