Glycogen phosphorylase is regulated by phosphorylation, binding of allosteric effectors and by the catalytic mechanism. https://www.ncbi.nlm.nih.gov/books/NBK22354/

glycogen phosphorylase and AMP

allosteric activator graph

the way I approached this was that it didnt increase the amount of substrate to reach vmax so it couldnt have been any kind of comp inhib, also the efficacy is the same so it couldnt be an allosteric inhib

Allosteric activators influence enzymes by inducing conformational change at the active site, which increases binding affinity for the substrate. This is reflected by a decreased Km.

AMP a breakdown product of adenosine triphosphate, is generated in states of fasting and thus upregulates glycogen phosphorylase to liberate stored glucose and supply the cells with a substrate for glycolysis when none is nutritionally available.