Just for consideration I would think about what type of riding I might do "as well as" the one tour. And the comments about gearing are spot on. Probably more important than tire sizing etc... as many bikes can handle the road conditions but the gearing will determine if you enjoy it.
Here's two pics of the same bike, an endurance 2x drive train and two wheel sets - 700c x 28mm and 650b x 42mm (road/gravel). I'm pretty happy with the 2x system for touring, having added a lowered geared cassette and flared bars. To me the four main things to consider are: 1. Gearing appropriate to the activity. 2. A comfortable cockpit. 3. Attachment points appropriate to the activity. 4. Wheel sizing ability appropriate to the activity. In my case I was able to flex my bike by retrofitting rims and cassette.
