Sure CB-Flygon is more effective if you can predict every move right but that almost certainly wont be the case.
Id say both sets (mixed and CB) have their perks and i think mixed Flygon is easier to use and thus should be placed for CB (easier to use in: has recovery, doesnt need to predict to beat Skarm, etc.).
Physical Life Orb Flygon is pretty bad though (tried it and honestly its only advantage over CB/Scarf is Roost... and Fly is better of hitting hard and fast than trying to stall something out), because it has problems breaking through common defensive Pokemon (Gyarados, Rotom-A, etc. pp. So either take it out, merge it with CB or just put it last.
Screech doesnt deserve its own set a mention in OO/AC (idk which one) should suffice. And yeah i tried it - it was shit.