

Plural elves has been the standard before Tolkien: https://www.websters1913.com/words/Elf
As for dwarves, this is what Wikipedia has to say, with reference to P. Gilliver et al. The Ring of Words: Tolkien and the Oxford English Dictionary:
Modern English has two plurals for the word dwarf: dwarfs and dwarves. Dwarfs remains the most commonly employed plural. The minority plural dwarves was recorded as early as 1818. However, it was later popularized by the fiction of philologist and legendarium author J. R. R. Tolkien, originating as a hypercorrective mistake. It was employed by Tolkien for some time before 1917.[6] Regarding his use of this plural, Tolkien wrote in 1937, “I am afraid it is just a piece of private bad grammar, rather shocking in a philologist; but I shall have to go with it.”[6]

























Admittedly this is on LOTR memes comm, so a little bit of fantasy is surely permitted ;)