Has it ever been explained as to how humans in the Dark Souls universe can grow to be so fucking huge?
Is it like the Wild Hunt Elves from the Witcher universe?
Yes, actually. It doesn't apply to the player because From gets lazy, but the more souls a human consumes increases their height and build. That's why Vendrick is massive, before you came along he was the most powerful man in the world.
Giants are giants in the sense of your typical fantasy.
Almost typed Phantasy.
Dark Souls lore is over the line Warcraft-teir when it comes to insane world and character origins and history.
Only difference is the game is more linear and there is no plot for the player, except what fans make up.