A few thoughts
re disc brakes and qr wheels. As an owner of such a bike, you're really going to need to become familiar with your avid bb5 or bb7 brakes. I have bb7s and if unfamiliar with them, you're going to have to spend time learning even the basics, such as proper wheel insertion for not rubbing the rotor. Even setup properly with well positioned calipers, my experience shows that one has to eyeball the rotor and make a tiny nudge so when t you tighten the qr, there isn't contact.
personally being able to deal with this, the unlikely chance of having to straighten a bent rotor, changing out pads etc is pretty essential when in remote areas.
All this was a learning curve for me, 30 years touring but first time with discs about years ago. It was sometimes frustrating, but necessary to go through this and become competent.
on the plus side, my bb7s work great and work fine for my loaded touring. Pad life has been great too but that is entirely dependent on your braking habits and conditions.
Re tubes vs tubeless. Everything I've read about the divide route shows that the southern section would be ruthless with tubes due to thorns.
I have no experience with tubeless but am very aware that there is also a big learning curve of how to deal with certain issues that can come up, so again, a lot of pre trip familiarizing and being realistic of how to deal with potential issues when out on your own and problems could be serious.