1. Answer: It depends on everyone's taste and these rankings change all the time. According to RankMyPorn, at the moment, the top ranked Under 30 Female Pornstars in the world are: Autumn Falls, Brenna Sparks, Katie Morgan, Monique Alexander, Rae Lil Black, Mia Malkova, Veronica Avluv, Eva Angelina, Kagney Linn Karter, Yurizan Beltran, but these will change based on what people vote.
2. Answer: It changes. You can see the latest rankings on RankMyPorn.com and also vote on it for free.