Whatever size you get use Schwalb Marathon Plus. ONLY ... The chance of not going 7,000 miles is slim to none.
Carry a spare anyway. I drill for schrader the second I get new rims. I was in Vietnam and China 4200 miles and saw only one 700c by 35 tire, in Ho Chi Minh. There was an American style LBS there, run by Americans of course. The mail duty gouge was 40%. Chengdu had a full Specialized store.

The local new derailler bikes seemed to be many 27.5". That is like 650B 584mm ??
Rohloff and chain case is the way to go. I had zero nail flats. Maybe I just have a good eye, evaded 50 or so. ha