Slash27,
On your first point I have no idea. I've not really been in the CT, or AH for that matter, much in the last year. All I had to go on was the situation as it was when I was here and then the Allied squads were both larger and more numerous.
On the second point, I think the P-51D will be harder to deal with than the P-38L. The Ki-84 is likely to be faster than the P-38L and P-47D-40 down lower and maybe even up to mid altitudes. At high altitude all the US aircraft will continue to be dominant as I said.
The P-51D is the closest to the F4U-4, but it doesn't climb as well and isn't quite as fast. It is also a little more fragile. The F4U-4 is a true monster.