I'm glad you were able to add the class to add the border to your contentWrapper. But for future reference, you should be able to select the ContentWrapper div in the layout structure and add the border.
In regard to your second question. Sculptor V2 includes different rounder corner layouts which you can use as a starting point to create custom rounded corner layouts.
In addition, you should be able to add divs within the extension which will allow you create more advanced layouts and gives you the ability to be closer to the finished design, instead of customizing the page after it is created.
