I disagree - an AP course isn’t about its exam. You should only self-study if you want college credit or if you’re interested in the course (AND it is not offered at your school). Colleges cannot care less about self-studied courses; it adds next to nothing to an application. Rigor varies between schools and I really can’t imagine OP’s counselor not checking “most rigorous course load” on the Common App because they took AP Lang instead of APUSH. As others and myself have pointed out, AP Lang can give you some lifelong skills in your writing or, at least, help in writing for college apps and other classes. I think you can get the same knowledge from a regular US History class and APUSH class.