The answer to your first question is answered here. Both are good low-cost ways to get started in macro photography.
Autofocus is not very effective as you near 1:1 magnification. Most AF systems will struggle to find focus, you have such a narrow DOF anyway that holding focus is very hard. With anything that is not moving, you are far better to set up a tripod and use live view to focus, if you have it. Or manually focus, then move the camera to and fro to get the subject in focus.
If you have a macro lens, you may not use it at 1:1 as often as you think, in which case AF can be very handy. I use it when shooting bees - it's very hit and miss, but for me slightly more successful than manual focus.
If you use extension tubes or reversal ring, you will be forced to be a certain range of distance from your subject (you can no longer focus over a wide range of distances), so AF is not really useful at all.
Aperture is important. You have a very narrow DOF, so you will often want to stop down in order to get as much DOF as possible. Or if you are shooting hand-held you may need a wide open aperture to avoid blur. If you reverse a lens, or have manual extension tubes and aren't able to control aperture, it's not a killer blow, but it isn't ideal.