OC Story Worldbuilding

Humans and Elves are the same species, just specialized for different environments. The majority of what sets them apart are cultural differences, not biological ones. 

HUMANS
The most populous, and most adaptable, humans are just what it says on the tin. Most human societies rely on agriculture, as opposed to elves who are largely hunter-gatherers.

Human cities and settlements can be found all over the map.

ELVES
Largely forest-dwelling, similar to humans, but more magically inclined, and far more magically sensitive. As opposed to humans, Elves continue to be hunter-gatherers. 

-CAVE ELVES
--So sometimes you get cursed. And you have to live in the mines. And your skin turns grey. 

-INK-BLOODED ELVES
--While it is a common misconception, Ink-blooded elves are not a subspecies of elves, but it is a blood disorder than only affects elves. It's said to be a curse placed on children conceived out of infidelity, but it's really just a genetic disorder tied to the same chromosomes that shadow magic is. It causes the growth of horns, makes wings grow in as leathery bat wings rather than the insect-like wings most elves have, and turns the blood black, which is what it was named for. Other symptoms are analogous to beta thalassemia.

HALF ELVES AND ECT.
Half elves half ears about half as long as a full elf (who would have guessed!) and roughly the same magical inclination as humans. 

1/4th elves and 3/4ths elves have noticeably longer/shorter ears than their full human or full elf counterparts, but roughly the same magical inclinations. 

Afterwards, the distinction becomes insignificant, someone who's 1/8th elf would just be seen as a human with slightly pointy ears, someone who's 3/8ths or 5/8ths would be seen as a half-elf, and someone who's 7/8ths elf would just be seen as a slightly less magically inclined elf.