You can do that just fine for Atmos. Yes M3's all around would be the best atmos setup but I still believe in a proper center. And bookshelves in the rear is usually not practical.
M3's in ceilings for tops. Aim the tweeters to where you sit
. M60's/vp160 up front, and go with a direct firing speaker in the rear like on wall or in wall...not qs8's. IMPORTANT - Keep the rear's at ear level. It'll sound great.
...and post pics! Room starting to look really good.
Looking at your pics, I'm thinking you are going to have the same issue I had, my pot lights are where my top speakers should be. I had to being them closer in, and it's not ideal.