But I'm used to the ST1100s in all sorts of conditions so the ST1300 was not a big deal for me.
I absolutely agree you can go anywhere on the ST1100/1300. I intend to bring my ST1300 over to the Alps in 2022 if COVID doesn't derail my plans. I ride all the little 1-lane narrow roads I can find and fully expect to so do on my ST. I've had my wife on the back of a "fully" loaded RT several times in the Alps for 2 - 4 weeks at a time, a relatively top heavy experience requiring extra care at slow speeds, gas stations, parking lots, etc - but we rode all the little roads I ride when solo on a BMW 800.
I would simply say that there is no question in my mind that riding a bike like Daboo's F800GT on the tight Alpine roads works every bit as well as a RT or ST1300 for touring and is a lot less fatiguing due to having a lot less weight to muscle around. I ride everyday when I'm in the Alps and I come back from Europe a LOT more worn out after 4 - 5 weeks of riding a 1250RT than I do a F800GT. I can see it in my tour members too who come from the States and rent 1200/1250s or the BMW K bikes. After a 2-week tour riding twisty mountain roads they're all ready for a break, whereas I'm onto my next tour group with my F800. The big bikes all work well in the moutains, but they are a lot more work. I expect to have to pace myself in 2022 if I ride the ST1300 all the time. I bought the 2018 Goldwing for here in NH because it suits the roads. I've enjoyed some spirited riding on it on the curvy back roads of NH and VT, but I would never buy one if all my riding was in the Alps. As mentioned earlier "different parameters in the different environments".