Coin went to Earth at the end of Sourcery.
He didn't exactly create another world, but went off to live elsewhere. On Earth (or Roundworld, I believe it's called?) magic isn't real, so it makes no difference that Coin is a Sourcerer. He may still have a chance at a normal life in a non-magical world because of his youth.- Jossed by The Science of Discworld: Earth was created by a different magical event at Unseen University
Rincewind grew up in The Shades, or at least another part of Morpork.
Rincewind normally tries to run away from any sort of conflict. His last resort happens to be a half-brick in a sock. He couldn't have gained his street smarts anywhere but the streets themselves.(He was born in the Mended (then Broken) Drum)- It is explicitly stated that he grew up in Morpork. He doesn't seem cutthroat enough for the part of the Shades that he and Conina visit, but FWIW the entire neighborhood isn't monolithic; he might be able to survive to adulthood around Cockbill Street (where Lupine Wonse grew up).
Coin is responsible for different characterizations after Sourcery.
He saw that Ankh-Morpork was a center of the world vulnerable to the wizards and other manipulations, so changed the world to make it safer and more wizard-proof.- Vetinari's wit was sharpened, or at least he gained more of a push to shape and control the city
- Coin chose Ridcully and company to replace the treacherous dangerous wizards of the past.
- The new Bursar was fragile-minded and unambitious, unlike Spelter
- Galder Weatherwax probably was instead born a woman, who was named Esme. That would also fit with how disturbed Granny Weatherwax is by seeing the possible world where she was a man, if that man was as disconnected and cruel as Galder.
Coin won't be completely lonely
Someone as powerful as him could almost certainly create friends in his little world to keep him company.- Or else he used his magic to go right back and start again - seeing something of the future of Roundworld and how it organises itself, he chose to reincarnate as Adam in a small village in England. thus allowing him to call back to his time as a powerful Wizard, even if as Adam he was unconscious of this.
