So many options it is hard to know what would work well
I had a Panasonic shiatsu massage recliner that was very helpful for my whole back and neck. I got a nice used one.
I used a far infrared heating pad , these heat deeper than standard heating pads, as well as other benefits.
I found IFC stimulator to be helpful. Much better than a TENS.
Interferential current machine - Google Search

The percussion massagers seemed too hard or too hard to hold and use on my own neck. Shoulders.
The heated shoulder, neck things seemed more of a comfort vs a healing thing .

This was back when I had the severe RSI/ TOS symptoms so I was wanting healing products. I still have and use those same products when needed.
After all these years there could be some new gadgets too.