I have been experimenting with something called a Posture Medic. posturemedic.com
If your posture is not the correct one shown in the picture below, a device such as this could impact nerve issues in your neck and spine by improving your posture. I know it has an impact on my posture which impacts my heart rate. Chiropractic adjustments have helped a lot but I still get AF occasionally. My heart rate becomes problematic when I stress my back in some way or maintain poor posture for too long. Staying on a computer or similar device for too long will do it.
Using this device has changed my symptoms further. Only using it one week, changed my back in a way that was noticeable to my chiropractor even though I did not tell him that I was using it. My wife says my posture is better. By shrugging my shoulders or manipulating my back a bit, I can change irregular beats to regular ones. Standing straight with by back and bum and head against a wall will increase my heart rate.
If I catch the AF just at it starts, by running on the spot for a minute or so will stop the AF. If it starts and I don't catch it right away, then going for a brisk walk for 30 minutes always stops it. When AF tries to start when I am laying down, changing my position will often stop the irregular beats. The key for me is to change my position as soon as AF wants to start and this will usually stop it. I determine if AF will start by feeing my wrist pulse. I can also feel a change in my back that will indicate that I need to change my position or manipulate my back. I know from what the pulse is doing, if my heart is in or will go into AF.
There is definitely something going on with the nerves in my neck and back. Perhaps if you are willing to try something like this device, you may find it affects your heart; and if it does this, then you will know the nerves in your neck and back are part of your problem. If you eliminate the nerve problem, maybe your AF will stop or become less troublesome.