I think not having kids would be the only real predictor, but even that isn’t perfect. Some girls can have kids and still be tight, and other never were in the first place.
As a woman who has a had a kid, mine did loosen up a little. I was so tight before that sex was never fun for me, until I met an exceptionally small guy. After, my gym said it was like I hadn’t had a baby, but I could definitely tell I wasn’t as tight as before. Now, I can enjoy normal sized dick, and bigger ones if they are slow and don’t put me in crazy positions! This is nice bc I prefer it deep and I’d never have found a guy w a pencil dick :P. I think not being comfortable in crazy positions also has to do w being petite. There’s not a lot of room in there. I’d think it would be better to be w a girl who is a little bigger, and can enjoy the kind of sex you like.
Also, I wonder if streach marks and baby belly would be an indicator. That means a girl’s skin doesn’t recover well, so maybe her pussy didn’t either. Kids also tend to affect a woman’s body more if she has them later in life, vs in her early twenties. I rarely see a girl who had kids later w no mom body issues.