WOW, thats going to be a lot of info :-) The shape of the wings and tails on the model is simply a matter of copying the full scale. On the full scale vesions there are of course different theories as to why one leading edge is straight and one is tapered. My knowlegde is limited on this but I will try and pass along what I have learned. On the Extra for example, the wing is tapered in the LE and TE. I believe this was done to increase the roll rate. The wing area needs to be of a certain size to get the right wing loading. So to make it roll faster you increase the septh of the wing at the root and decrease it at the tip. The Edge series of planes have a straight LE and a tappered TE. I think this was done to make the wing stall easier hence tunmle easier. A wing with a straight LE will stall all at once. A wing with a tapered LE will not stall all at once and will be a more gentle stall.
Comparing the Extra 260 to the 300. The 260 has a shorter tail moment. This makes the plane better at some of the tumbling type manuvers were most of the 300s are better at IMAC type. Same with the Yaks. The newer model Yaks are longer and smoother. They are great at 3D because the wing loading is light and the control surafaces are huge.

As I said at the start I am no expert on these subjects. I mostly posted to get the ball rolling give what little I thought I know and give other guys a chance to agree or tell me I am wrong about my conclusions.

david