LEO lists only "which" for welche. I know that in relative clauses commenting on the whole of the sentence 'which' can refer to people.

(1) He looked like a thief, which in fact he was (was ...)

But in sentences with "welche(s)", I think there is a true attributive relative clause, so shouldn't it be "who" for persons?

Consider the following example sentence:

(2) In the following essay I am going to describe the main characters of the novel, [who or which?] are Mr X, Ms Y and Mr Z.

I think this is a special type of attributive relative clause: an apposition.
Of course, it's most natural to simply leave out who/which are but if one uses the particle, should it be "which" or "who"?

How do native speakers feel about this?

Thank you very much in advance.