Mi dos centavos:
I love those 49mm-thread Takumars, so I use a 49mm thread reversal ring to stack a short Tak prime (fixed-focal length) onto a short tele prime. To stack lenses with different threads, I could use tape (but I'm lazy) or a step-down ring (if I could just remember where I put it...) and as none of my zooms are fast nor 49mm, I haven't tried stacking with any zoom. Decent fast manual primes are still available for not much money. My basic assortment of 28, 35, 55 (secondaries) and 100 and 135 (primaries, non-Tak) cost me less than US$100.
Yes, stacked lenses have their objectives (fronts) facing each other, as close as possible, to avoid vignetting. And a bit more magnification can be squeezed out by putting the primary on extension tubes or bellows... with a further loss of light, of course.
By "reverse adapter" is probably meant MOUNT reverse adapter, such as a 52mm-PK ring. Some lenses gain some magnification by simple reversal, but most lenses just give better results on extension tubes or bellows if they're reversed. And of course the reversed lens can be any brand -- the mount doesn't matter, just be sure there's manual aperture control. I use such a setup mostly to see how a lens works at macro, or to reverse longer lenses.
Ease of use: a 1:1 macro lens, manual or auto, is easy and flexible, but getting beyond 1:1 requires stacking or long extension. Greater working distance requires a longish lens. Buying macro lenses, manual usually costs rather less than auto, and AF is useless at macro ranges IMHO. A new AF macro lens is a beautiful tool for many purposes -- but I'm a cheap bastard, so I'll stick with my good cheap glass.
As for microphotography vs macrophotography vs photomicrography vs photomacrography... see Wikipedia.
"There's more than one way to skin a cat," she mused,
as she pinned its little feet to the dissection board.