How did you narrow it down to these?
6.5’ is pretty low, but I think you’ll be ok. How much room behind the listening position(LP)?
I have a pair of rc85i in one of my rooms and to my surprise they’re pretty darn good. Especially for the price. The main thing for tops is wide dispersion, but finding that spec is basically impossible for IW speakers. I used rsl c34e’s for my Atmos install. The baffles are on 15° so aiming is pretty easy. They also have aimable tweeters which I find useless but the option is there.
For spacing, with the lower ceiling especially you’ll want to keep the speakers as much in a square above you as you can. Like this...
45° in front and behind.
Height locations on the front wall, and back wall(or side height) can be good alternatives.