I think those RSLs look great. I wanted slightly smaller holes so I got some Canton ceiling speakers from A4less and at that time the RSLs were out I think. But the Canton's sound really great too so no loss there. I considered 8" Cantons but they advised for Atmos content I wouldn't have much difference so settled for 6.5s and they worked for my ceiling. I would agree though to not buying crap if you intend to stay in your house for a while. It's really a small difference over time
I think you made a great choice. Canton makes excellent speakers so I’d be comfortable with them too. And yeah, I think RSL had a backlog for awhile. I believe they were filling existing orders while building the MkII.
As far as the 8” goes. Atmos speakers do receive full range signals, so having more capable ones can be advantageous. Practically speaking though, you might not notice.