In a 2 column page using the [col2] shortcode, is it possible to change the widths to make one column wider than the other?
Yes, you can create 2 column of different width in a fullwidth page by applying the code showing below in a page editor. Code: [col2_3]This is content...[/col2_3][col3_last]This is content...[/col3_last] for the reference, see below image : and see the link for more detail: http://inkthemes.com/wptheme/blackbird-technology/columns/