Category and tag page are archive pages and X provides two style and layout options for archive pages. If you go to X > Launch > Options > Blog > Archives, under Style, you have Standard and Masonry. Under Archives > Layout, you have the option to use Global Content Layout or Fullwidth. Global Content Layout will display a sidebar if you chose a Content Layout with sidebar in Options > Layout and Design.
Here's a sample of the Masonry style http://demo.theme.co/integrity-1/blog/. Here's a Standard style with sidebar http://demo.theme.co/renew-1/blog/. Ethos has it's own unique layout http://demo.theme.co/ethos-1/.
If those doesn't meet your needs, you'll need to take a look at Essential Grid or The Grid which are bundled in X. For more details, please visit the links below.