It would have been helpful to see a proposed floor plan or at least some room dimensions.
I’d avoid in-wall speakers unless for some reason you have no other option.
The rear speakers should be on the side walls ~3-4 ft. behind the listening position, at least 6-7 ft. up on the wall.
If possible the front left and right speakers should be spread the same distance apart as the main listening position is from the screen.
A dedicated electrical circuit for the equipment is a good thing to have. This will help insure that you don’t get interference (read hum or other noise) from things like light dimmers. Make sure plenty of outlets are installed in the equipment closet for all the gear.
You didn’t mention a powered subwoofer, but you need at least one even if you have to wait and add it later. Typically the best location is at or near a front corner, so make sure you have an electrical outlet there and a wall plate for the signal input. Might go ahead and do the same thing for the other front corner, in case you decide to add a second one later.
Make sure your speaker and other wiring is rated for in-wall use.
A common mistake made with wall hanging TVs is to mount them too high. The TV should be at eye level, or no higher than slightly above eye level.
Regards,
Wayne A. Pflughaupt