Cannot comment on Kim Kardashian, but as far as I remember from watching a bunch of random documentaries and such, Paris Hilton's "dumb blonde" public persona is just an act, and she indeed scored pretty high on SAT.

Cannot find any sources at the moment other than tabloids and blog posts, but I recommend checking out a fairly recent documentary on Netflix (either 2020 or 2019, I forgot) that talks about "influencers" and such. Paris Hilton got a giant segment dedicated to her on it, and she indeed was extremely articulate in her description of that whole "dumb blonde" public persona schtick. After watching it, I had zero doubt that she was indeed a very intelligent person, despite me having zero interest in her as an entertainer or a public persona.