Best Plex setup for Dolby Atmos

Hi,
I hope I'm not upsetting anyone by choosing this forum, but after searching, reading and digging through all the other content I could find on this topic I'm now more confused than ever before!
Here's my question: I just upgraded my system after many happy years with Plex and a 5.1 setup on an Onkyo SR875 receiver. My new gear: Onkyo TX-NR1030 (Atmos and much more-capable), a brand-new MacMini (fully loaded: dual thunderbolt, i7 processor, etc), 20 TB LaCie RAID5 with identical drive as backup, 7.1.4 Atmos speaker setup, Sony SXRD Projector).
Needless to say, after that amount of money I want to get the most out of my system, including Atmos "sound" from .mkv files appropriately configured. What is the best Plex setup to achieve my goal (of course I have been a Plex Pass member for many years, so I could get Media Player, but how do I need to configure it to get the right should from all 12 speakers ???)
Many thanks for your time - it's appreciated more than you can imagine (I guess you can tell my frustration).