Atmos: Non Ceiling Speakers

I tell u what, speaker placement is always going to affect relative sound quality vs seating locations and overall room layout and associated acoustics. Still, to be true, probably less sound coming from these "filler" speakers, so not as critical to overall performance wise, as compared to mains, say.  And, yet, I think following the general guidelines for these speakers, as per dolby.com website is going  get you in ball park, and then take care in following aiming guidelines, either ceiling reflecting or above and to sides for ceiling speakers, pointing down in between/towards seating locations.  But as I said, beyond the theory of dictated recommended locations, still, placing speakers in poor sonic locations, WILL degrade the response and tonality propagated from the loudspeaker and, ideally, will not sound as good an accurate as it should (try cupping hands around mouth and speaking, or placing speakers in holes in response, in corners for too much bass, etc, and understand this. -MANDATORY EQ CIRCUIT, REGARDLESS!). But, again, no full range sounds from these atmos speakers, but rather limited filler info and steering ques and so forth, likely.
Always going to be compromises, and less than idea choices will exist.
Trial and error and isolating one single speaker probably always  the best option if you CARE about what kind of sound is coming from EA loudspeaker!   MOST people do not take that kind of care, so then simply follow dolby.com for atmos fer your config, and then maybe move em around and listen and see how well they envelope, don't distract or draw too much attention and are hard to locate. 
Actually, I have hard time believing most will go through hassle of running so many speakers all around the room! Probably overkill anway. I mean I guess you could put hundred speakers all around the room, and EQ every channel!  Then again, where does it all end, I say.  Quality of placement and setup first.  Then maybe add a pair and experiment.

Sounds reasonable and common sensical.  That is a rare thing in audiophilia

I'd probably default, yeah, to integrated atmos speakers ontop of other speakers, for convenience, if I HAD to have that, over putting lots of speakers up on ceiling, unless it was an all out dedicated theater!?  Few have that, nor makes sense to wire speakers everywhere. I think there's plenty of envelopment, myself, with 7.1, personally!
Also, I have been a long time advocate of placing front mains up higher towards the ceiling, say 2 or 3 feet off ceilng- opposite of 2 to 3 feet off floor for monitors or floor standers -  just like what you 'd experience in a commercial cinema, for presence and envelopement!  Works excellent!  something to consider and play with. 95% of everyone is going to keep em down low, like for typical music setup, though.  For dedicated move setup, I won't hesitate to do the oppposite, and just work on getting excellent sound from ea speaker location from seating. 
Still, regardless, I want best sound first, then more sound sources as a priority further down the list.  And, in the end, everyone has different gear and setup anway.  Which ones are correct setup, correct equipment, best results???  It's all up to personal opinion and situational by enlarge