Given the option as an 18-yo male I’d probably opt for 5% male, but that’s strictly a matter of personal preference, and not a basis for admissions.
I endured 75+% male and didn’t particularly enjoy it, but that’s not why I attended my similarly-sized engineering college. I went for the education and rigor.
Caltech is and has always been about hardcore study. It’s not a cotillion. At least it didn’t used to be.