I'd look into the Topeak Trunk Bag DX or DXP, along with the MTX racks. They have a decent capacity, and you can collapse the side bags and use it as a regular trunk bag when you aren't touring. With a light load, putting weight on the rear should not make a big difference to bike handling. Topeak also makes some good handlebar bags.

If you are credit card touring, chances are you will be near many places to get water. A few liters of capacity ought to be sufficient.