You're less than an inch away from my height and inseam. I'm about 5'4" and a half.

54 cm is too big. 52 cm, maybe. ~50 cm is probably your size. It varies a little bit based on model, but 95% of the time, a bike that fits you best will be between 48-52 cm.

If you're sticking to road, find a bike that uses 700c wheels. Salsa Vaya and Fuji Touring are good options, at different prices and levels of quality.

As far as touring goes, essentially the only advantage to 26" wheels is availability in third-world countries. I've found that in most of Latin America, get to a larger city and you'll find shops with 700c wheels/tires/tubes. The next large city is usually no more than a week away, and there are few tire/wheel issues that can't be mended for a week at a time with a boot, spare tube, and a patch kit. Can't speak for Africa or Asia. You can always carry a spare tire if it's a long tour and you're worried.

I'm not familiar with Kona or Scott, so I'm no help there.

Disc brakes can be nice, but aren't wholly necessary, especially if you're sticking to pavement.

In summary: If you're sticking to pavement in developed countries, get 700c. Even if you're not, 700c is fine as long as you're prepared. Your frame size is ~50 cm. Disc brakes are optional.