sounds like you could do this without panniers with gear within the airstream of bike. Actually a small front rack would be a good idea for a 12liter sized drybag to balance out the weight somehow strapped/secured between rack and handlebars near the head tube than cantilievered out like most handlebar bags. The ability to carry LOTS of water will be important so the front bag/rack will be another place to strap a 20oz bottle besides three on the main triangle.
When I was your age and weight I toured down from SF to LA then took the train up to Redding then road down to Tahoe and back through the valley backto SF, with about 15lbs of gear all on a road bike that didn't have eyelets or fenders. But then it never rained and I didn't take a tent.
I rode with 700x28 tires. I don't think there will be much benefit to making the bike superlight or spending money on "nice components" given that the biggest difference for moving fast and light will be the amount of gear. I'd go for fast 700x32 tires just for the comfort of smashing through any rough roads.