Exactly what others have said, I would definitely opt for 6-prongs for safely (for bigger stones eg 1.5ct up) & definitely wouldn’t look busy if done delicately. Attached photo of my 2.14ct for ref.
I'd say six for a 2+ carat diamond because four creates a square look that I'm not crazy about. I see prongs more as a necessity to hold a stone in though, not pretty in themselves, so I don't see the reason for double prongs.