Absolutely key to keep this as simple as possible. Less things to fail, also - cheaper. Out of the options shown, I would also choose the last drawing, although there are other options as well. Let me make a quick sketch in paint.
Only one tensioner, pushing up away from the wheel. Idealy there would be more chain wrap around the middle wheels sprocket, but this was just to show one other, simpler option. regardless of your setup, chain stretch will occur, just plan on shortening your chain at some point.
Note: Disreguard - this was not thaught out.