You are basically right, the brakes, just make sure they are very tight with some thread locker. Unless you have an ebike motor you don't need a torque wrench to build a touring bike. Torque wrenches are important when you have to get beyond "as hard as you can crank it" and if you have to make sure you don't over tighten something to the point it causes damage, or if vibrating parts etc. I think you answered your own question.

Having said all that, it's not like lower torque wrenches are expensive! I have one and use it because it's fun and makes me feel better.

Also, holy crap, that bike looks like it has a case of boss-itis.