In general you need a rigorous schedule. But there is no paint to taking something that is not right for you. So one class is ok but if you took a less rigorous schedule in general it would absolutely impact you.
As you know any Ivy is a stretch for all. It’s great to have the goal but do realize last year Columbia admitted 6.3% of applicants. I believe this year was less but don’t see data posted.
You will experience a lot of changes and learn to understand more about college in future years.
My point- don’t fall in love with any one college. Be the best you and in two years you’ll find a whole set of colleges that can and will work for you, whether it’s Columbia or otherwise.
Getting good grades and take the right classes for you, not a school. No point in getting a bad grade etc
Good luck.