Colleges are not going to be impressed by an online AP course. They prefer students to take AP classes at school if possible, and they like to see high grades ideally. If you do an online course in the summer, you can’t take the test until May. That’s a long time to wait to take a test.
If you are looking for college credit, you have to do the test. By all means, do an online course if you want to go for credit, but understand it isn’t going to help you get into a college. You can study on your own and still take the test, so it is possibly just wasted money to do it online.
I recommend self study or online study for AP courses when the school doesn’t offer the subject and you want a score that will either give you credit, or allow you to place out of intro level courses. I don’t recommend it to impress colleges.