Touring is a ball. Just a ball. While I don't follow the touring forum and while I'm not a thread categorization purist, I will note that Bike Forums has a dedicated touring forum which will probably give you a lot more varied inputs. Fish where the fish are!!

Regarding CS length... I find its almost entirely a matter of heel clearance. It depends on foot size and rack/pannier combos which vary. I've got really big size 13 feet. I get heel strike with 43cm stays. It's close but workable at 44cm. For me, 44cm is the min. Some will argue that you get more stability with longer stays and 46/47cm stays have been used (early 80s treks) but 45cm seems to be the agreed upon norm now. Lastly, you can get tire clearance issues with stays in the 43cm range. On my bike with 43 cm stays, I can get 30mm tires in there but am flirting with tire rub.

Regarding road triples and gearing.... I find that when touring, speeds are low and small variations in road surface or incline make huge differences in the amount of power needed to move forward. So, I really prefer to have narrowly clustered gears in the mid range. No need for big gears as downhills mean coasting, not racing. And then really small gears for hill climbs on the granny.

Regarding the difference in the gearing on the Bruce Gordons versus Trek 520s... IMO this shows that BG is focusing on pure tourists while Trek understands that many people by 520s for commuting and other purposes. I'll betcha Trek sells more 520s.