Do overdieties run polytheistic pantheons through power or just authority. Do they have actually that much more strength or just have the highest governing power?
Ao writes the rules but is it through strength or is it a power of the office?
What exactly is the difference between "having strength" and "having the office, which has strength"? No one can challenge Ao because Ao can write the rules. Anyone who tries to oppose his rules gets destroyed--even gods.
We very clearly see the head deities of various polytheistic pantheons slain, overthrown, replaced, and merged with other gods. Odin was expected to die in Ragnarok; Zeus slew his father Cronus, who had slain his father Ouranos before him, and would have been slain by his own son Hercules if he had not learned from the lessons of Ouranos and Cronus. Ra went through eighty-bajillion mergers/facets (Amun-Ra, Horus-Re/Ra-Horakhty, Khepri, Khnum), but even when he was seen as the creator-deity, he was still a deity
like Isis, Horus, etc. as demonstrated by myths where Isis forcibly coerced him to reveal his true name so she could put Horus on the "throne." Even Ahura Mazda, one of the closest things to an "overdeity," is not as absolutely powerful as is logically reasonable--he must contend with Angra Mainyu/Ahriman and the forces of darkness.
Ao, on the other hand, is entirely above all of that. There are no beings of any sort that can oppose or question Ao (other than the vaguely-alluded-to "being of light" that is apparently Ao's boss, and explicitly on a rung higher still). He has no divine domain, no portfolio, exists in no pantheon, determines the nature of deities and the rules that govern all forms of deities, and his power can obliterate anyone or anything that tries to oppose his rules.
Zeus, Odin, Ra, etc. are almost exclusively recognized as "heads" because they are considered the wisest or most powerful of beings that are of the same class.
Primus inter pares, in a certain sense. The overdeity doesn't
appear to have most, if any, of the attributes associated with that class of being--to the point that the overdeity can
decide what the attributes of that class is, without having that reflect on the overdeity too. If that's not enough to distinguish them, I dunno what is.