Those are just “names”: students all take the SAME classes at Columbia. But if you’re 18-22 you have one access pathway, and if you’re older, you have another access pathway. So, if OP wants the Ivy league and likes the idea of attending Columbia + living in NYC, CGS is his pathway. Classes, majors, level of selectivity are the same.
They look for the same characteristics, intelligence, intellectual vitality, diligence, kindness, resilience, originality… but rather than high school classes (which may or may not be relevant to mature applicants), the CGS process looks at what the person has accomplished in addition to HS. (Good grades are required, pf course. But nonlinear applicants are evaluated on way more than that as proof of the aforementioned characteristics.)