I've got to love the people who comment here without having toured fixed.
I've toured fixed. With two rear panniers. With the same sort of load I would normally ride with. Over similar distances and terrain I would tour with on a geared bike. With front and rear brakes. With my standard MTB shoes and clipless pedals. Without issues with knees or anything else.
The simplicity is wonderful.
Ask me some questions relevant to your ventures, and I will try to answer them. From my experience.