not quite correct Canberra. The USAF wings are the same shape but the difference is what is in the middle. The pilots wings have a shield, WSO's have a fist grapping what looks like lightning bolts. Other categories have different symbols again. (It is impossible to tell until you are about 2 feet away).
The RAAF Nav full wing was introduced mainly as a recruiting measure, there was too much feedback that the single wing was seen as a big negative. The only RAAF navigators at the time who rushed to get one were WGCDRS and above in Canberra (desk jobs!). We had a petition running around as well but were basically told it was supported by the chief so dont bother fighting it.
As far as blues and drabs, drabs have always been optional.
The reason I thought the RAF dont wear wings on their blues shirts was so they could comfortably wear a flying suit over their uniform
Saved time on a shower when time to go to the bar!