In choosing a fertilizer, is the overall ratio of N-P-K important or
the individual amounts of N, P, or K the sole qualifying factor?

For example, "Root Stimulators" have a high phosphorous but near-null
of N or K.

Another example: Bloom or leaf stimulators have a high amount of
nitrogen and little P or K. So is it the ratio of N to P to K? Or
amount of a single component N that makes the leaves grow and flowers
bloom?