U need to do a lot of searching and reading I don't see many people handing u a tutorial with a wealth of info in here wheb all u gotta do is click sear and type dwc. Its easy stuff just put in a half hour of web surfing and ull be off to lowes
If you use one container you will have roblems if you need to pull one or more plants as the roots will grow together.
Air pumps... 1 really big on or 1 medium one for each. It's hard to have to much air in your water. I am sure there is a limit, but have yet to hear that someone had to much DO in their water.
Multiple tanks take more effort to maintain. There are trade offs.