@Lindagaf Yes, I have heard about college credit courses. I was debating for a while whether to take a Columbia CC course, but ultimately decided against it (although I could have easily gotten the recs). The tuition is pretty extravagant ($6k!), and as you mentioned colleges don’t view you more favorably for taking it. Plus, I’ve heard from elsewhere on CC that the course isn’t actually selective/prestigious-- yes, they require teacher recs, but they accept most people who apply because they want the money. Not to say that the courses aren’t fun/interesting, though.
I am already going to a math program by NYU for 3 weeks in the summer, too. While Columbia’s doesn’t strictly overlap with it I would have to put in a lot more hours of studying throughout the morning/night.