Two primary factors to tightness of a vagina. The woman's hip size and number of natural child deliveries.
My first time was with my high school girl friend. She was beautiful. A top athlete, swimmer, soccer, and tennis. She had amazing muscle tone. We were both each other's first. Her build was built for babies as an uncle used to say. Wide hips and a full chest with large D cup breasts.
I remember fingering her the first time and being surprised how easily I was able to get inside of her vagina. Save the jokes, we knew each other since we were five years old, I know I was her first.
When we had sex the first time she was very wet as you would expect, but more surprisingly her vagina was not very tight at all. I'm the same as the OP in my anatomy so that's not the issue.
The next girl I was with was a spinner, 98 lbs, 17, I was 16, about 5' tall. When we tried to have intercourse, it was almost impossible to get inside her.
I have found these two rules to be very true for my experience over many years and a number partners.
This is not an empirical study in any way.
