I want to allow my non-HTML-savvy clients to create and edit content but am still trying to find ways to do that while maintaining the responsiveness of the site.

In particular, there are cases where they want content to be in 2 columns and I'm not finding an easy way to allow them to do that through the WYSIWYG without using tables (which would break the responsiveness).

In general, it doesn't seem like there's any way to add DIVs or apply classes to things like Unordered Lists. Does the CKEditor make this easier? Are there any other suggestions on how they handle this?