My wife and I have used
Topeak trunk bags and racks for the past 7 years. The attachment system is incredibly easy to use. Just slide the bag on and it locks. Push a tab to unlock it, slides it off.
They have several styles of bags, including one with fold down panniers. The panniers are cloth, so they'er not going to carry real heavy or sharp objects, but they are more than sufficient for general utility or light credirt card touring.
I have the standard MTX bag. A typical load includes tools, snacks, a jacket and camera. Leave out the camera and jacket, and it can hold a half gallon of milk, or bottle of wine, or a couple of reasonably sized books.
My wife has the MTX with fold down side panniers. On utility runs, she can carry 2 loaves of bread and 2 half gallons of milk. The bag + panniers has enough room to pack all she needs for a three day credit card tour.
More
Topeak bags and
Topeak Racks from the Topeak web site.
The Topeak Explorer MTX rack has a 40 lb limit and is suitable for fully loaded touring with standard panniers. For loaded touring, the Explorer MTX rack does not have room to hold standard panniers and the trunk bag at the same time. If you want to carry both standard panniers and a trunk bag, the Super DX Tourist has the additional mounting rails.
Some examples of the bags and racks on my Surly LHT and my wife's Jamis Aurora:
{The standard panniers are Arkel T42 and T18}