It is my understanding that they sound very similar in the mid's and high's. The inwall/onwall version might give you a tiny bit more in the lower end because of the bigger enclosure that sits within the wall.
Carpentry wise, the onwall versions are much easier to install as the only cutout is the small hole where the speaker wire comes out, or you could use the Axiom flat adhesive wire that is paintable and you would not have to disturb your walls.
I tested the onwall 22's to my regular M22 bookshelfs some time ago, and the larger M22's put out the lower frequencies better, but if you have a sub that will help fill in that gap when you go with onwall or even inwall/onwall.
I would not be to concerned about using the 100 or even 150 centers, they sound very similar to all the variations of the 22's and mounting below the TV I think would give you better results considering your seated/laying/inverted position.