Choosing moderators is about their judgement first, and their skills second. Making someone a mod is not a favour to them, or a promotion, or a simple act of friendliness - it’s giving them power over the community.
In particular, anyone who posts while angry, or tired, or under the influence, is inflammatory, or argumentative, would for me be a poor choice of moderator.
Ideally you will have set out what your culture is, how you expect people to behave, and how you expect moderators to cooperate.
I would say you should have the minimum number of moderators which can handle the load. Ideally there’s very little to do, but you might like to have people in different time zones.
You do need good members who can start interesting conversations, and keep conversations on track, and answer questions constructively - but that’s not the role of a moderator.