There's a lot of wiggle room for elf ears between Spock ears and WoW handlebars. When I did my concept sketch for high and wood elves, I made their ears about a hand in length. That's certainly longer than Vulcan ears.
As for differentiation between elven subraces, YES, I want them. A good place to start is -- I dunno -- their written descriptions? High elves are pale, with raven hair and green eyes. Wood elves are tanned, or downright brown, with brown, red or dark blonde hair, and green eyes. Gray elves (also called faerie elves in 1e and 3e, and called eladrin in 4e) are pale, with silver or blonde hair and blue or violet eyes. That's a lot of differentiation, right there.