Thanks for reaching out and welcome to the community!
Do you have a recommendation for a wall mount as we would like to wall mount them.
There are a few ways to mount cameras to walls, but I always have to put out this warning first...
It is very common to get vibration/shaking in camera shots when the camera is mounted to structures. Buildings move more than we think, and the optical zoom on cameras like the XA series will easily reveal any vibrations or movement coming from the structure they're mounted to. Having been down this path many times with other churches, schools, governments, and businesses, it is actually so common that it becomes an issue more often than not.
And while there are some mounts that help alleviate these issues, they almost never solve them completely. The only real solution I've found that actually works somewhat decently are the Nigel B Designs mounts. Even then, they haven't been able to solve every problem.
So, I say that to say: test it thoroughly before making any purchases or final decisions. And don't be surprised if you find out that mounting to the walls will not be possible. It happens.
Now, if you find that mounting to the walls will be doable then I probably recommend using L-shaped PTZ mount brackets like this: Sony Wall Mount Bracket for BRC/SRG X and SRG PTZ Cameras. I like these types of brackets that have the added angled supports on the sides to give the mount more rigidity. Keep in mind you'll possibly end up having to drill a hole or two in the plate to mount the Bescor heads.
And no matter what, I would advise staying away from mounting arms. They will be less stable and could possibly cause more issues with vibrations or shaking. You'll want something pretty rigid and stout to have the best chances of stable images.
Also, is there a remote available in the market to power on/off the camera?
Yes. I recommend the VariZoom LANC remotes. They tend to be the most consistent and reliable. I have the VZ-STEALTH-LX and have personally tested it on the XA series. It works great and has control of power on/off from the remote.
You will also need LANC extension cables. I recommend the VariZoom cables as well or the ones from NSI: