Since 3e, the core difference in story between the warlock and sorcerer is that the warlock patron is waaaaaaaay stronger.And I'd argue that they're effectively the same thing and whether the demon you got your powers from is your boss or your grandad is a matter of character background, not mechanics.
Sorcerers came from dragons, minor celestials/fends/undead or freak accidents.
Warlock came from Arches and Elders. Archfey, Archdevils, Archangels, Demon princes(ses), Elder gods, Archliches,