Hey there,
I could be wrong.. fairly newb myself, but from what I understand, topping and scrog are different techniques to achieve similar ends. IE. i dont see why bother topping if you are going to scrog anyway.
In topping, the point is to get 2, 4, or even 8 main cola's. While (as i understand it) the plant is more or less left to grow normally.
in Scrog, the point is to not have a main cola at all, but for all your buds to get equal share of the light, and therefore have all similar sized buds and greater total yeild.
If I'm incorrect, please let me know. Just my 2 cents.