Regarding elven ethnicity, I am perfectly willing to allow creative license on this point. We’re talking about immortal fantasy creatures. Being consistent with real-life human genetics and evolution is a low priority. Particularly as there’s nothing in Tolkien’s source material that strongly defines elves as exclusively fair-skinned. The mentions of fair skin are limited to descriptions of particular individuals, and the Noldor race of elves. I do think that Tolkien probably conceived of elves as white in his own mind’s eye, but he never committed strongly to this in the text.