I would recomend the last setup (your third picture). That is the same as the drivetrain we had last year and we had zero problems.
Our first year we tensioned our chain by moving the wheel axles, and it didn't work well at all. Chain tensioners are not as much of a hassle as they are made out to be, and if they are done right they work very well.
Here's a picture of some of our tensioners from last year.
What kind of transmissions are you using?