Eärendil and Elwing: Appearance and Height
But yet Eärendel was an infant; and he was a child surpassing fair: a light was in his face as of heaven, and he had the beauty and the wisdom of Elfinesse and the strength and hardihood of the Men of old; and the sea spoke ever in his ear and heart, even as with Tuor his father.
- The Shaping of Middle-earth: Quenta Noldorinwa
I think this description implies that Eärendil looked more like his mother, Idril.
but Elwing the fairy have all poesies named as beautiful as Tinúviel if that indeed may be, yet hard is it to say seeing the great loveliness of the elfin folk of yore.
- The Book of Lost Tales II: The Nauglafring
It's not asserted that Elwing indeed looked like Lúthien, but it may well be that she did.
(iii) Eärendel was smaller than most men but nimble-footed and a swift swimmer (but Voronwë could not swim).
- The Book of Lost Tales: The Tale of Eärendel
The word men was not capitalized, so it could mean that he was either smaller than most human men or most elven men. Regardless, he probably wasn't considered tall by either standard.
Let's look at the height of his family.
Very fair and tall was she, well nigh of warrior’s stature, and her hair was a fountain of gold. Idril was she named, and called Celebrindal, Silver-foot, for the whiteness of her foot; and she walked and danced ever unshod in the white ways and green lawns of Gondolin.
- The Shaping of Middle-earth: Quenta Noldorinwa
Now Turgon himself would appear, ‘tallest of all the Children of the World, save Thingol’, with a white and gold sword in a ruel-bone (ivory) sheath, and welcome Tuor.
- Unfinished Tales: Of Tuor and his Coming to Gondolin
She[Indis] was not of the Noldor, but of the Vanyar, [of the kin >] sister of Ingwë; and she was golden-haired, and tall, and exceedingly swift of foot.
- Morgoth's Ring: Of the Laws and Customs Among the Eldar
Tis written that in those days the fathers of the fathers of Men were of less stature than Men now are, and the children of Elfinesse of greater growth, yet was Tuor taller than any that stood there.
- The Book of Lost Tales: The Fall of Gondolin
Galdor and Hareth had two sons, Húrin and Huor. Húrin was by three years the elder, but he was shorter in stature than other men of his kin; in this he took after his mother’s people, but in all else he was like Hador his grandfather, fair of face and golden-haired, strong in body and fiery of mood. But the fire in him burned steadily, and he had great endurance of will. Of all Men of the North he knew most of the counsels of the Noldor. Huor his brother was tall, the tallest of all the Edain save his own son Tuor only, and a swift runner;
- Unfinished Tales: Narn I Hîn Húrin
Thereafter Húrin son of Galdor ruled the house of Hador in Dor-lómin, and served Fingon. Húrin was of less stature than his fathers, or his son after him; but he was tireless and enduring in body, lithe and swift after the manner of his mother’s kin, Hareth of the Haladin.
- Silmarillion: Of the Ruin of Beleriand
Many of his[Hador] people were like him, golden-haired and blue-eyed; they were tall and strong, quick to wrath and laughter, fierce in battle, generous to friend and to foe, swift in resolve, fast in loyalty, joyous in heart, the children of Ilúvatar in the youth of Mankind.
Like to them were the woodland folk of Haleth; but they were shorter and broader, sterner and less swift.
- The War of Jewels: Of Men
In conclusion, it's safe to say that Eärendil inherited the smaller stature from his great-grandmother Hareth of the house of Haleth. I think it's befitting that Eärendil shares the traits of all his ancestry.
Elwing's height wasn't mentioned in any material, but if we take into consideration her ancestors' height.
Then his folk gathered about him in joy; and they were amazed, for fair and noble as he had been, now he appeared as it were a lord of the Maiar, tallest of all the Children of Ilúvatar, his hair as grey silver, and his eyes like unto stars.
- The War of Jewels: Grey Annals
Beren the Renowned had hair of a golden brown and grey eyes; he was taller than most of his kin, but he was broad-shouldered and very strong in his limbs.
- The Peoples of Middle-earth: Of Dwarves and Men
On the basis of lack of contrary evidence, Elwing could be very tall as well, even taller than her husband Eärendil.
