If I understand the question correctly, no need to use CSS to do this. If you create a a GPP Layout Element, choose Content: Full Width (no padding) and Display Rules > Location: Page > All Pages. This is for those of us who don’t fully trust our CSS skills 🙂
Is this functionality that you have available at this point? Rather than full-width by default, I’d like to change the page builder container to Content/Sidebar by default on blog posts only. Do you have suggestions for how to implement this?