“Prep” school is a college preparatory school, but now commonly refers to boarding schools. A number of boarding schools have post-grad programs for students that have graduated high school but want an additional year of high school for various reasons (athletics, test prep, academics). With your grades, classes, ECs and test scores, you are a good match for the top prep schools , but you’d have to really talk to coaches to see if you’d get playing time at QB. Most of these coaches/schools are good at marketing their athletes. I know there were a bunch of college coaches that did a tour of the boarding schools last season for scouting.
Pros: another year to be seen, good marketing, can really beef up your application with even more advanced classes, good transition to college (although you don’t seem to need that).
Cons: More expensive than college, while boarding school feels like a lot of freedom to 14/15/16 year olds, at 19 you will now be dealing with a curfew, study halls, etc., not conductive to a part-time job or additional ECs outside of those offered at the school.
Additional considerations: Unless you were planning a gap year, you will be doing a concurrent application process of both boarding schools and college. The only upside of that is that it gives you an option if you don’t like your college options after acceptances come out.
Chesire Academy has a good football program (our neighbor committed to Duke from there). Here is their PG (post-grad) info. https://cheshireacademy.org/academics/signature-programs/postgraduate-pg-program/