Mayo makes more sense as a DC. Ran a 3-4 most of his career though and while that doesn’t mean he’ll have to run one it is an odd fit. Usually guys who run 3-4s believe in them. Having said even that whether it’s 4-3 or 3-4 most teams rarely run a base set anymore for most of the game
Nickel is probably the most widely used set at this point. If that’s the case the only difference between a 3-4 and 4-3 is do your ends stand or have their hand in the dirt lol