Posse only covers tuition. Unless UPS meets need for Posse scholars (I don’t think they do, but look into that), you would have to pay for room and board. Plus travel, books, incidentals, etc. If you would have to pay room and board, UPS won’t be affordable, so you might consider stopping the Posse process now.
Are you applying to Oberlin, whether thru QB or not?
Have you taken physics? If not, are you taking it senior year?