The CSS styles feature in PowerCMS 2 is the same as it was in PowerCMS 1. We are trying to work out a solution where you could reference your website's style sheet to have all the styles available in the HTML Editor, as well as applied to the content when displayed in PowerCMS.
Unfortunately, the fckeditor which our HTML Editor relies on doesn't accommodate for CSS style sheets in a way that would make this implementation very easy - but we are considering ways to handle this in the future.