I was thinking about maybe taking an AP class online and transferring credits, like maybe AP Music Theory? Yeah I was considering taking a fun class like ceramics or whatever but I thought it would bring down my GPA so I didn’t go with it. Ideally, I wouldn’t have dropped anything but I was worried about being overloaded and not being able to get the A’s I should be able to get.
AP Music THeory is very difficult and requires you to have a background in music already.
@dontknow123 Said gently - maybe you should stop obsessing and spend your time focusing on what you can control 
You keep saying you think colleges will frown upon a free period. You are looking at your schedule and seeing a free period. Colleges aren’t looking at your schedule and seeing open blocks. They are looking at a listing of your courses (common app) and will then will be looking at your transcript which also just lists the classes. They will see 6 courses listed. Rather than trying to add a class because you think that adds more substance, spend more time working on your AP lit work so you can raise the grade. You have a rigorous schedule set up but colleges want to see how well you do with it so work hard to get the B higher.
As for AP online courses, if it is a reputable course, it can be very time consuming. Keep that in mind. Consider that if you spend 5 hours a week in class at school and then how much homework you do for each of those classes and that is about the amount of time you can anticipate spending. That doesn’t fall in line with taking a “fun” class. My son has two friends that took an online AP Music Theory class junior year and they never imagined it would be so hard. Good luck!