For English, post-AP courses could be more in-depth literature courses (commonly taken by English majors) or more advanced writing and communication courses (not necessarily about literature – e.g. writing about science).
For history, frosh/soph level courses are not sequenced, but can include courses on areas not found as AP courses. For example, you may find survey courses on various countries or regions in Asia, Africa, or Latin America. Junior/senior level history courses are commonly more specialized, such as the Byzantine empire, history of US immigration, history of science, etc…
Depends on which liberal arts. Science definitely. Economics definitely. Other social studies, depends on if you go heavy into quantitative and statistical analysis. Humanities, not really, except that if you take math courses with proofs, they can give you practice with logic that you may encounter if you major in philosophy. Math courses with proofs can give general practice with logical thinking that you may not get much of in many majors.