1. Answer: It depends on everyone's taste and these rankings change all the time. According to RankMyPorn, at the moment, the top ranked Straight Female Webcams in the world are: hotfallingdevil, ashlyeroberts1, iran_persian, letiziafulkers1, c4price, scarlett1_, marianacruzz, yum_yum_, abie_owen, raquelle_star, 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.