Are MagSafe 3 cables compatible across MacBook Air and Pro?

Yes, they’re compatible. Apple standardized the MagSafe 3 connector starting with the 2021 MacBook Pro and the M2/M3 MacBook Air. Power output depends on the charger, not the cable — the Air will only pull what it can handle, but the Air’s charger won’t top off a Pro as fast. So go ahead and swap cables.