How do you pack 3 weeks of stuff into 4 panniers?
Short answer: don’t bring a lot of stuff.
We each have 4 pairs of bike shorts, socks and exercise shirts. We each have something nice we can wear to church. They have to serve double duty if we go out to eat somewhere nice. We each brought a puffy and a bivy sac, which we hope not to use - our plan is to stay in hotels, Airbnb, and normal bed and breakfasts. If we ride according to our plan, we won’t be sleeping under a park bench. (Fingers crossed.)
We are using bike shoes that have low profile clips, so they can be our normal day to day sightseeing shoes as well. We each have a pair of flimsy lightweight loafers we can use for nicer venues.
Toiletries are at a minimum. For the first time TSAs regulations were not the limiting factor.
The balance of our free space is filled with snacks and tools.
Laundry is going to happen along the way. We have a clothes line that we can string up on the back of our bike, in case we need to make it more obvious we are tourists.
We squeaked through check in at the airline with both bike boxes weighing 2 pounds under the 70 pound limit. That was without our large panniers in the boxes - those are going with us as carry ons. This is one heavy rig.