The "true" answer is, Elves are imitating Humans thus are Human height.
The English "small elves" are actually fairies. In his descriptions of English folkbelief during the Renaissance, Shakespeare describes the fairy as a childlike spirit. They looked like human children and were the small size of human children. Notably, similar to the way that many angels can dance on the head of a pin, because they are spirits, these fairy children were also able to shrink but to about the size of a fingernail, not as small as an angel could shrink. Later during the Romantic Period, artists imagined the fairies as small adults, and as spirits of nature used iconography with insect wings analogous to angelic wings. Because elves were understood to be a kind of fairy, in the sense of a magical creature, elves were often referred to as fairy folk, or fairies. In some places, the term fairy and elf were interchangeable. Hence, some small or tiny fairies were called "elves".
But the original concept of the "elf" as appearing as an adult human of full human size continues to persist, such as in places in Scotland.
Elves look like humans. Odd features such as wolf ears relate to their shapeshifting magic, or the an artistic iconography relating them to nature.
In sum. Elves are essentially human in appearance, albeit often an idealized version of a human.
In D&D terms, the "santa elves" most closely approximate Gnome, also a kind of fairie, a small sprite. In the UA, player species are normally Humanoid, but I hope to see the Gnome as a "Fey Humanoid".