I can't imagine needing to carry more than 40 pounds, because like I wrote, I backpack in the wilderness for 10 days with that, and it all fits into a 55L pack. On the bike, I wouldn't be 'credit-card touring,' but I'd be going for fewer than 10 days between 'services.' I think panniers would be better than bike-packing bags since they hold the weight lower, make access to items easier, and probaby go on and come off the bike more simply. I do note that there are packs and racks that attach to non-traditional touring frames that lack braze-ons.
I note the long chainstays on the LHT. For sure it would meet all my needs, but since it's not the most available or affordable thing, I'm looking for alternatives to consider. I could simply use a pannier that's shorter front-to-aft, even if I had to use front panniers on the back or sew my own bags. I might do either of those things anyway.
The need for low gearing is a serious consideration. The places I want to tour can be incredibly steep. This pretty much rules out original-equipment boom bikes like my Schwinn or that Bianchi 12 speed. The lowest chainring they have on the crankset is like 40-something teeth. I figure I'd need a 3x9 gearset or at least a 2-by with a big cassette. There's a nearly new LHT for sale in my size, but it's been built with a 1-by geartrain, has no racks or bags, and the seller is asking $2K. I'd have to re-do the whole groupset and there wouldn't be any cost-savings in it for me compared to buying brand-new.
I know 36 spoke wheels would be more than tough enough. I think the 32 spokes on the Disc Trucker would be more than enough for me. Like I wrote, I'd have a hard time being much over 200 pounds for bike, gear, and rider. Other folks are much more than that without any gear. I might not want the lightest carbon race wheels, but I figure pretty much anything else of good quality will be fine.
I agree fit is important. I'm not willing to go out on my Schwinn that's at least two sizes too big -- not for a multiday or weeklong tour. I've done a couple days on it before and suffered the back pain. So if I have to get a new-to-me bike, my doubts are about how happy I can be with something that isn't totally tour-specific and what I will want to avoid. At some point, I'll stop "overthinking" it when I find a good bike in my size and after a couple tours will know. In the mean time, I'm just hoping to get some good advice to learn as much as possible the easy way.