Self-studying AP Environmental Science or AP Computer Science?

Hello! So my school does not offer either of the courses above, but I am interested in both of them. I have two questions:

  1. Which class would you recommend? I have an equal level of interest in both but which one would be less difficult to self-study? Please share your experiences if you've taken one of these classes outside of school.
  2. How would I go about self-studying for either class? Would I need to take an actual online course or could I just work out of an AP test review book and take the AP test in May?

Thank you for your time!