Personally I don't get why folks like to ride in boots or sandals when cranking out long miles, but I guess it is a matter of personal preference. I much prefer a pair of bike shoes with plenty of mesh for good ventilation, drying, and drainage.
Sandals are superior to your biking shoes for everything you say is important to you. Sandals eliminate the use of mesh entirely. So sandals provide great, not good, but great ventilation. Great drying. Great drainage. Mountain bike shoes have their place. Such as when mountain biking and you might hit your foot on a rock or tree or crash. And they are better than sandals when you might hit your foot on something. When I tour I don't hit my feet on stuff. So sandals are superior to shoes for touring.