IMO he is an Eclipse.
Wiseman, Chronos, and Commander I think are types of NPC Overlords that appeared in Yggdrasil. So to classify a Player Overlord into one of those three archetypes isn't going to cut it.
If we were to describe Ainz's abilities in such a way, than he would lean over towards the Wiseman side (With some Chronos in there). Ainz can summon undead, that's for sure, but he doesn't have much in the way of unit control or buffing abilities that the Commander would use.
Theory time:
1) It could be that in the New World the three archetypes are mixed or meaningless. Ainz couldn't keep undead around in Yggdrasil but can in the New World. In the New World such things might not matter that much. Also Overlords are almost unheard of in the New World, so to the population this would just be a small difference in ability. (I don't like this theory after typing it out, but brainstorming is about listing bad ideas with good ones.)
2) Yggdrasil had many secret features and hidden classes. Ainz's Eclipse class has some very specific requirements in order to achieve. A player might not reach these requirements if they tried going for one of three archetypes above. So it could be that Ainz is in a less known, but existent, forth archetype.