he said for prince among thieves he told the rappers what to rap about. what the story was and what he was looking for from each of their characters.

one of the interviews was this one, cant remember what the other one was
https://music.avclub.com/prolific-producer-prince-paul-on-almost-being-fired-de-1798237198

AVC: So that beat works because it fits the demo theme. How much of the rest of the production on that album changed to fit the lyrical themes of the broader story?

PP: That one, the hook happened to work for that particular song. But initially, for the rest of the album, I just told MCs what to rhyme about. It was like “This is the concept, rhyme about the concept.” I lucked out because they figured it out. They understood it and were able to write toward that, and then I would just produce the song around that, whether it was the hook or sound effects or whatever other arrangement to make it work in the story.

looks like on Negroes On Ice he did write raps with his son but definitely seemed like that wasnt a normal thing for him. so yeah i guess he has an idea or concept and will tell rappers what he has in mind but will also work around what rappers want to do and do what he can to enhance it.