I am not sure there is any one right area mode Max, it depends on your target bird and how near you are to it. With really fast flyers like swallows and the like a wide AF area like Zone 15 or 25 pt zone helps a lot, also I use all pts sometimes which really helps to capture a fast erratic flyer - when using one of these modes it also helps to use to correct 'Case'. The only trouble with using a wide AF area is that the AF will pick up on the nearest part of the bird which may be a wing tip and not the head/eye, this is especially troublesome when the subject is fairly close.
With AF point expansion you can easier put the focus point over the head/eye although picking up really fast and erratic flyers is not always that easy even with 8 pt expansion.
I would rarely use just a single point for BIF but of the other options IMHO its a matter of choosing the best one for my subject considering flight speed, flight characteristics and subject distance. One of the beauties of the 7D2 (and most other Cams) is that it is very easy to change the AF area mode on the fly while still looking through the viewfinder.