Columbia generally has the smallest class sizes in the Ivy league. Over 82% of the classes are under twenty students. Other than some freshman introductory classes, classes will be small. Yes, you can double major or major and minor, you just have to take the required classes to satisfy the requirements. I guess you have to decide whether you want to apply to the College, or the School of engineering.
Thanks @ricck1 1and @integer , I am assuming you’re majoring in cs at columbia seas, here is another question: is taking a chemistry class(es) required for you? (Considering its a part of the core.) Thanks again.