hau Perry,
As you have probably gathered from the previous posts, there are many ways and each climate has a best method.
If you are going to be drying herbs indoors (as in inside your home) and if you have air conditioning, then bundles will work because the humidity is reduced by the air conditioning.
If you are drying outdoors in high humidity but also have good air flow, then the tobacco barn type drying will work great too, the air flow reduces the dampness and the bundles slow the drying process so all volatile oils remain where they are supposed to be.
If you are in high humidity, stagnate air type areas (low air flows) then you might be better off with single stem or just a few stems to a bundle.
In most "tropical" areas (lots of heat, high humidity, low air flow/ no winds) then you can get great results with a
solar dehydrator, incorporating light color fabric(cotton) sheets between layers will work nicely to get great results with a dehydrator.
Bundles are for speed and ease, plus almost no one needs just one stem at a time. My wife uses about 4 stems per recipe she is making.
Bundles have been traditional as the method of drying herbs since at least the time of the ancient Greeks.
The best method for drying herbs is the method that works best for you.
Redhawk