I mean the reason the new winglets work now and not before is that the wingspan needs to fit in the 80m box. The design now allows that. Before it did not.
The 80m rule is why the 77x will fold it's wingtips.
Separation in the air is based on weight. The 748 is a code F but does not need the same separation as a 380. Approach is dependant on stall speed. 380 is Cat C but a 773er is cat D.