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.
When installing quick release wheels with disc brakes, it’s best to set the wheel on the ground and set the fork on the axle ends. This ensures that the fork tips are properly seated on the axles. This is also the best way to install the wheel on
any brake system with quick release.
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.
BB7 are fine brakes. As to pad life, I have yet to adjust a disc brake pad for wear, even through I’ve been using mechanical discs since around 2005. Some of that is my constant changing of calipers due to upgradeitis, but a lot of it is how I use my brakes. I don’t change pads on rim brakes all that often either.
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.
Tubeless on bicycles is one of those items that has a lot of misconceptions associated with them. Tubeless tires aren’t any more or less prone to flats than regular tires (or, more correctly, tubes). Mount a tubeless tire dry on a bike and go for a ride, and you’ll experience as many flats as tubed tires with the added joy of harder flat changes and repairs. The sealant is what makes tubeless tires seeming impervious to flats. You can put sealant in tubes as well and enjoy nearly the same imperviousness.
It’s probably not something to worry about until Cuba, NM as most of the route is in the mountains where goat heads don’t grow (too cold).
On the other hand, if your bike is tubeless ready, there probably isn’t a downside to running tubeless on this route. I don’t personally run tubeless because of the care and feeding necessary for tubeless…regular refreshing of sealant, the messing mounting procedure, the need of a compressor, the extra weight, the need to repeat all that for the 11 bicycles in my garage, etc…but when using a single bike over a long period of time, those are smaller problems.