Botha wasn't the most talented fighter, far from it, but he was one of the toughest and fearless. That said, he is "made to order" for Wilder.
Wilder by a brutal KO. As limited as Wilder is, you still have to have certain attributes on point to beat him.
Probably Wilder but I wouldn't write Botha off either. He could box, he was tough and he had decent power. Look at what Duhaupas did to Wilder despite having light firepower himself. Ortiz should have a win over Wilder too but they gave Deonkay like a 10 minute rest when he was in trouble
This is getting silly. Please take a look at what Lennox Lewis did to the guy. I know Wilder lacks the skill set of Lewis, but he had (just) enough skills and more than enough power to get the job done.
Botha would probably be roughing Wilder up for a couple of rounds before Wilder lands his right. Then Botha would take a nap. Hard to predict which portion of the fight it would take place in, but that would be the general pattern of the fight.