The specs may be the same, but I can tell you from experience with pre-production models that the M22 on-walls do not have the bass extension of bookshelf M22s. I suspect the in-walls have better bass. I would probably choose the M3s, because of that hump. Perception is, well, how we perceive, right? And how we perceive is important.
Airplay is for streaming from iPads/iPhones/iPod touches or computers running iTunes. The music may be stored in the cloud or it may be on the source device (ie, the iDevice or the computer). If you store the music in the cloud, you would be using (and would have to pay for) iTunes Match, which I can tell you from personal experience works pretty well. But the Airplay device cannot stream directly from the cloud. Unless it's an AppleTV box, in which case you wouldn't be using Airplay per se.
