Interesting. Ayton is a significantly better defender than Collins, and Ball is immeasurably better on that end than Young. Ball is also (stunningly) the better 3 point shooter over his career, let alone over the last two seasons.
Young is obviously the most dynamic player of the four, but I think he'd potentially struggle with how much less usage he'd get here alongside the Jays compared to in Atlanta. Collins is the ideal 4 next to Horford, but he'd be the fourth option on the court in that lineup, which I don't think suits his ability to score efficiently.
I'd probably go Ayton and Ball. They seem to fit Udoka's philosophy of a defence-first attitude, and they're great team players. It would also be infuriating watching Trae play defence. Worse than IT