Looking for suggestions for wall mounts for the Axiom QS4 v3 that would go well with them please.

The power bracket is the standard mount: https://www.axiomaudio.com/power-bracket

There's also wall and ceiling mounts that'll work which I can no longer find on the site (and links to it from the speaker pages give a 404 error); so if you have a need for a non-flush mount I'd call Axiom and ask about these:
https://www.axiomaudio.com/full-metal-bracket
https://www.axiomaudio.com/full-metal-ceiling-bracket

Hmmmm, you’re right… the FMB & FMCB are not currently listed. These were very high quality bracket but also very expensive. I suspect they weren’t a big seller.

In all my applications (M3ow’s hanging from the ceilings on FMBs & M3’s from ceiling on FMCBs) I needed special inserts added to my speakers to use them.
Which ended up costing Axiom a couple of round trips to get right. Perhaps another reason to drop them.

Didn't realize they weren't on site any more. Really glad I ordered a few extra pair for anything I add down the line.

I've gotta believe hanging OWs from the ceiling is an outlier; whereas mounting bookshelves on a wall is much more common and would be bought on a regular basis. Plus, weren't they just all excited about a second "molding" machine? I'd think they could produce them on-demand with that beast.

And Yeah, I have a couple spare I bought too; but just those two, I'm sure I'll be wanting more at some point.

Axiom mentioned they will have a restock of the full metal bracket later in the year

I can use the Power Bracket for a wall mount? Do I need to buy any tools besides a drill?

How high should I mount them on a 9 foot ceiling with windows on the back wall?

The power bracket will work. Try to hit a stud so you don’t have to use wall anchors. Probably about 2 ft from ceiling is where I’d start. If you have a way to shift them up and down without mounting to the wall first you can try different heights and see what sounds best

7 foot high is a good height for ATMOS rear speakers?

You really want monopole speakers for Atmos because they’re directional. Using quad pole speakers like the qs4 the mounting location is variable. You can certainly try them lower but I’d keep them above ear level.

As canesfan27 pointed out ATMOS needs directional speakers since it’s trying to place sounds in 3d space. The QSx speakers are designed for 5.1/7.1 where the intent is to provide ambient surround sound

How well will they integrate with as a 7.1.2 channel if I use them with KEF R11 for L/R, KEF R2C Center, and 2 KEF R3 as the rear surround?

If you were trying to integrate them into that array. I would do the r11 for L/R the R2C for the center, the r3 as your left and right surround and the QS4 as rears. The side speakers in the 7.1 will get more of the sound than the rears in most applications. I switched mine from 5.1.6 to 7.1.4 and the bulk of the sound was always from the side surrounds more than rear in both layouts. Axiom makes floor stands for the QS series speakers if you want to place them in a more traditional 7.1 arrangement if you have room for stands. If they are going on the back wall i would experiment with height placement.

Shandoeluna, KEF is making decent albeit pricey products nowadays, something that wasn't true 10 years ago. Loudspeaker measurements are publicly available, and the layman is now equipped to call out manufacturers that don't deliver.

You'll be fine with any of the surround speakers from Axiom if they're positioned according to Dolby's recommendations. I'm not sold on 7.1 as a meaningful upgrade over 5.1, but it doesn't hurt to try it before hardwiring it into a permanent setup.

I agree with you on 5.1/7.1. Most titles I’ve experienced use the surrounds for general ambient … rain,thunder, explosions and such …. 5.1/7.1 does this very well. With 7.1 giving a bit more control in general direction (which doesn’t get used too often). Very few ATMOS movies, even today, really do much more.

Would a 5.1.4 set up be better than? There is no room for them to be put directly behind the sofa in either the family room or the game room if I was to move the set up there. The wall would be 14 feet from the TV in the game room. The family room has 20 feet of space from the TV, but the issue is that due to the awkward placement of where the master bedroom hallway door and fire place means I can't move the sofa up any more or either the sofa or the speakers at floor level will block the walkway. I can't mount them on the wall behind as there are windows and curtains covering the entire wall. I can mount them on the side, but the side near the fire place would be much farther away than the other wall side which is very short before it opens up into the breakfast room and back door. Upstairs the game room opens up to a 40 foot long entrance hallway to the front door with 21 foot high ceilings before it becomes 10 foot in the game room at the balcony so can't side mount them on the wall.

I am kind of considering buying some KEF R8a though as it seems easier to have them mounted on top of the R11 and R3 to bounce off the ceiling.

Before buying any equipment, it's probably best to decide on a permanent room configuration before poking holes in spots you'll later regret.

Directional speakers like the R3 are not as ideal as surround speakers that radiant across 180º and provide a non-localizable ambience. Mine are sitting on the floor rather than above ear level, and it works fine for my situation without having to mount or even look at them.

I have 5.1 in the family room. The surrounds are on the back wall only because of aesthetics. They are distanced asymmetrically from the MLP since 1/2 the room is taken up by the ping pong table and because the entrance will eventually have a barn door… but it works … 5.1 with QS surrounds is very forgiving… so do the best you can