Movement of the drag curve

[WannaBeBiggles]

Hi all

I have searched high and low for a good explanation for movement of the drag curve.

I'm primarily trying to understand questions such as:

Aircraft A and Aircraft B are the same type, travelling at the same altitude, at the same speed, in the same ISA conditions. Aircraft B is 20% heavier, what happens to the drag curve

Moves (and then combinations of UP, DOWN, LEFT, RIGHT)

Then going further, the same sort of questions but say Aircraft B extends LE devices, spoilers, gear or flap etc etc

I guess I'm a bit of a visual learner, so if anyone has links to graphs or can explain it in a straight forward manner, that'd help me out a lot.