re: I changed the width to 274 like you asked and now I have 3 columns so that is what I was looking for, so thank you very much!!
re: Which plugin would I use to have the categories listed across the top of the page instead of or in addition to the drop down categories?
None, actually. What they did was they filtered the list by category using the drop down and then copied the resulting URL from the browser’s address bar and put the links in manually above the shortcode.
Does that help?