Keep in mind, a lot of this stuff is gimmicky, concocted to generate sales of new equipment. For example, 7.1.6 that you mentioned, what is that for? To my knowledge, there isn't a single studio mixing 7.1.6 content for home release and you probably will never see it. Home theaters are "small rooms" studios mix content differently for home theaters than they do large commercial theaters because they know you can only fit some many speakers into a small room and they know that not that many speakers are needed in a small room to get the same effect as a large theatre. With that being said, 7.1. 4 might have been overkill in your room. Truth be told, Dolby Atmos is very difficult to do right in the typical home, most can't really implement it per Dolby's recommendation, overhead speakers firing down at the listeners in a small room. If you cut holes in your ceiling for speakers and it doesn't produce the results you expected, in the case with you, as you discovered, they might be too far apart, you are pretty much screwed unless you cut more holes in the ceiling to get it right.
I've noticed when some enthusiast set up a Dolby Atmos system in the home, some complain about not hearing enough information and/or sound or effects coming from above them. The sound mixers are not doing enough with the overhead sounds, so then they are disappointed. However, in real life, not that many sounds are heard about us, 90 percent of sounds come from side us and upward, not directly above our domes, that is why from a technical and practical perspective, Auro-3D systems made more sense for the home than does Dolby Atmos, because the Auro approach was to mix from sides and then upward towards the ceiling and not from directly above us, although in Auro-3D they did offer the single overheard speaker referred to as the VOG. So it's really good thing that they don't place that many sound directly above us because they could become gimmicky, unrealistic and destracting. Instead of immersing you into sound, thereby enhancing the movie experience, its taking you out of it.