Well here are your choices.
Either the circle pad or buttons can move Pit. If you have a CPP, that stick can also move Pit.
Touchscreen, touchscreen / d-pad, or touchscreen / buttons can aim (in other words, under two of the options you can use two different ways to aim).
You can then remap everything else to the remaining buttons. You assign attack, use power, select power (left), select power (right), change view (snipe), and align camera to any combination of L, R, X, A, B, Y, and each direction on the d-pad. If you have a CPP, whatever you assign to the R button will translate to the CPP's R button.
You can also change how quickly the aiming reticle moves during air sections (rails shooter), how quickly the reticle stops after starting to move it, and invert vertical and horizontal.
And then you can tweak similar settings for land battles - how quickly the reticle moves up and down, separately from how quickly it moves left and right, how quickly it stops after you start it moving, and invert vertical and horizontal.
It also has shot homing, aim assist, and autofire that you can turn on and off.
That's the long and the short of it.