Just doing some local testing... Using the Extended plugin options to float primary sidebar to the right has some odd consequences that are probably due to the "responsive" functions not expecting a right-positioned primary sidebar (I realize this function of the plugin is a work in progress).
1) If Secondary sidebar is present, it causes overlap of the post content (text and also post title background block) and secondary sidebar text content while shrinking the browser window to test responsive functions.
2) If Secondary sidebar is NOT present, any right-floated images within the post content sit way too far to the right (relative to the post text). If the window is being resized smaller, the black Primary sidebar will increasingly overlap the images until the responsive settings move the sidebar below the post. The text content of the post does not appear to be affected by this except in the #1 case above when the second sidebar is present.
In case #2, it appears that the image margins are treated just as if the black primary sidebar was never there and are based only on the right-hand edge of the page.