Before I answer your question, I'll briefly elaborate on the overlord species. Overlord is the highest race of undead who primarily have the appearance of skeletons. Just like other undead species, the overlord class is the final form of both the skeleton mage and Elder Lich class (most undead would have to gain enough levels to evolve through up to that point). However even within the overlord race, there are different levels.
According to the wiki: "Momonga has an Overlord racial level of five." Even though we aren't told exactly how many levels are within the overlord class. It makes sense to say that the higher the level within the overlord race, the more powerful the individual overlord. I'm guessing this makes Ainz Oal Gown pretty special when compared to the typical average overlord (more like the 5 overlords that guard the nazarick grand library, there is big difference between them and momonga in terms of power level and abilities). This could explain why he has characteristics of the 3 different types of overlords.
So to answer your question, Momonga is not an ordinary Overlord, his superiority in level among the overlord race probably gives him the advantage of being an overlord with abilities similar to all 3 types. ( He also has dark wisdom, allowing him to learn spells that he probably couldn't. This cheat ability makes him nearly invisible because we don't know for sure which specific spells he learnt from the dark wisdom ability) I hope that answers your question.