As the OP said touring styles are on a continuum from credit card to fully loaded expedition touring. I wrote something recently that tried to categorize these styles, but in the end there are as many as there are riders.
http://wheelsofchance.org/2009/08/19/touring-taxonomy/
love the layout. All the touring I did when younger was ultralight and the one time I used panniers they were like the skinny ones shown on your site. Riding where it didn't rain in the summer helped and I tried to find camp spots where I could get under cover.