I am a huge fan of early 90's rigid mountain bikes. No better climber in my humble opinion.
It's all about geometry as far as I am concerned but it has to be the right geometry for you. In other words how tall you are may affect what frame geometry works for you.
In my case at 5'-9" the smallest size MB-3 is the optimum tourer because of the seat height to handlebar relationship for ergonomics and the smallest Q factor.
I remember reading at the time that the MB-3 with the Suntour group was the narrowest Q factor. While it may be less costly than the Shimano components again Q factor and geometry for height is a hard combination to beat for distance.
Q factor is how narrow of a gap between your feet when they are on the pedals. The narrower they are the more athletic and therefore efficient the "ergonomics" is the way I understand it.
https://www.sheldonbrown.com/bridgestone/1990/pages/bridgestone-1990-07.htm
This bike as it shows up on the link is an extremely sturdy frame. I have pushed it past it limits on occasion and can personally attest to it's durability. It is easy enough to have any mounts you may need added but I believe it comes stock with front and rear for paniers.
That being said I am sure that the Surly company can make you a frame that is perfect for you but if you happen to fit a classic Bridgestone frame... and you have that built into a touring bike with that classic geometry, then I think you would really have something a touring bike that actually handles.
I am certain that Surly or other custom builders can make something equivalent or better but if you are between 5'-7" and 5'-11" and fit the Bridgestone frame I think this is the optimum tourer properly fitted.
There are quite a few Sheldon Brown articles to check out if you want to do a deep dive.
https://www.sheldonbrown.com/bridgestone/1992/1992.pdf
I remember when the first Kawasaki two stroke triples came out. My Uncle had a 1972 H-1 I got to put quite a few miles on. Seat of the pants experience concurs with what I have read about how those early kawasaki's in that they changed the classic geometry of the earlier triumphs and that it just didn't work. The solution ended up being suspension, travel, and then dialing in spring rate and damping but nevertheless that classic geometry for road handling stayed constant.
If a 26" diameter (or whatever custom wheelset will fit the frame) works for you a classic Bridgestone frame touring build would be a really nice bike. This would make an excellent handling road bike laden or not.