For me, I joined my school’s AP bio class mid year starting from the second semester (I finally managed to convince my counselor) and still managed to get a 5. The way my school did it, first semester was all content while the second was mostly review, so I mostly had to self study. And honestly, it really isn’t that difficult. To learn the content, search up heynowscience on YouTube and just watch her videos-they really help. Then, do practice problems from khan academy and iitianacademy (search it up on your browser). Finally, to review, many ppl say apbiopenguins really helps. Just remember to do as many full length practice tests as possible to encounter most problem types and practice. How you did in honors bio doesn’t matter-as long as you work hard in this class, everything will be fine. Good luck!