I tour mainly on paved roads on 32mm tires (gator hardshells). They do fine on canal towpaths, but not on stony offroad tacks.
I actually prefer a harsher ride, so I pump them to 7 bars.
I even toured for many years on 28mm tires.
I tried touring on Crete on 26 x 2,1 inch tires on an 80’s mountain bike. Same gear, but it felt like a tractor to be honest. I experimented with 4 panniers as well, just because, but nah, unless I need that extra volume someday, I prefer my drop bar set up.
