The antecedent in the urgent and attributive clause is a human conjunction. Which one would you use?

This usage is correct. Because antecedents emphasize identity.

Generally speaking, in attributive clauses, when the antecedent refers to the person, the relative pronoun is usually guided by who/that, and which is rarely used to refer to the person. But when the antecedent emphasizes the identity and status of the character, which one should be used instead of who?

Another example is that they talk like foreigners, although they don't. They talk like foreigners, but they are not at all.

Bill foresaw that he would become a cleaner, which helped him escape from prison. Bill pretended to be a cleaner, which helped him escape from prison.