Ok, I will take a crack at this. Why do you think there is a difference in spin induced throw between a thick vs thin hit? There are only 2 way that I am aware of to impart more spin onto a ball, force and surface area contact. First force; By this I mean the amount of spin the cue ball is able to transfer to the object ball. Spinning the CB faster will impart more spin on the OB.
Second, Surface Area;
When you increase the amount of surface area at the point of contact then more spin will be applied. Now since pool balls are made of phenolic resin and are very hard, there will be NO give in the balls during contact. So the surface area of the contact point is constant and always very small.
That being said hitting it thick or thin wont matter because the contact surface area wont change no matter how the 2 balls collide.
I have to disagree with this last statement. If you shoot 2 shots soft speed with loads of english it is clear that a thicker hit (say center ball to half ball cut)will throw more than a thin hit (less than half ball cut). So even though the contact area is the same the thicker hit will stay with the cue ball longer and throw it more.
As far as what english is truely more accurate i would wager bottom english. No left or right to throw it, and with the cue ball spinning backwards the object ball goes to a natural roll as soon as contact is made. If you used top english you would transfer some draw onto the object ball.