Actually, taper is the relationship of blank butt diameter to the tip diameter. This describes how much the blank "tapers" from the largest diameter to the smallest diameter. Taper does have an effect on action, but it is not the sole determining factor.
Action is how it deflects (bends) under various loads.
Power is how much load it takes to deflect the blank.
Blank speed is what percentage of the blank length deflects with lighter loads...before it gets into the "backbone".
HTH...