Atmos - direct firing. That is how it is designed, and why they are "matrixing" the overhead sounds with the front channels (they are direct) and not surrounds (which can be direct, or bi/di/quad pole).
Diffusing type speakers for overhead Atmos will suck. Plain and simple.
That is it in a nutshell, and for people with the attention span of a squirrel (not you, but some of the other rascals around here).
For more information, keep reading....
That is the biggest problem that experts are saying the speakers with an "Atmos module" on top of them has... It takes a direct speaker, plops it on top of your mains or even surrounds, and then bounces it off the ceiling. By then, it is so diffused that they don't think that you will get very accurate object placement in space.
Wait a couple of weeks. I am going to CEDIA. I already have some Atmos demos scheduled. So far the premiere setups (which most of them fall into this area) are talking about direct firing only. The less-than-premiere manufacturers are showing their "Atmos enabled" front speakers a lot, which are still direct firing speakers. I can give a report back on the speaker tech used for that.
If I had the cash, and if I was sticking with Axiom, I would get their new in-ceiling M3 speakers (4 of them if I am going to do it) and a serious receiver (have to be 11.2 to get me my 7.2.4 that I would want). Unfortunately, that is WAY more cabbage than I can spend.