"Wai" for people or things closely related to people (like names), so it usually gets translated as "who", but as "what" for names. "Aha" for things, so I think it always gets translated as "what", but can't be used for names, I think.
Technically, it can be kōna but it is not used really. I never hear it pronounced that way. The a-class kāna always has the kahakō, though. In Tahitian there is always the kahakō - tō 'u, tō 'oe, tō na, etc.