I was in a car crash about four years ago, the other parties' insurance company paid for physio, massage etc, I closed the case around Easter 2018, I still get quite a bit of specific pain but I suppose I've got that for life now - in my neck/shoulder and under my shoulder blade/spine. I was given exercises such as lie face down and raise your arms behind your back with palms up, then sit up straight in a chair and try to pop a imaginary ballon with a pin on your head by stretching your neck and spine only. The best exercise I got was from an NHS physio after the insurance fiasco was over. The best way I can describe it is to stand up straight and raise your arms directly above your head as high as you can, as if you're praying, then slowly open them into a crucifix position with palms up; then do the same while doing a small lunge.
My experience is..
Early intervention is vital. Insurance companies care about money. The NHS care about people. Physio can be a bit hit and miss. Massage can loosen things but it's no substitute for stretching. Massage done incorrectly can cause more harm than good. Ibuprofen does work (but it's not good for you!!). Free at the point of use is worth its weight in gold.
If I was paying for half a dozen physio sessions I'd drop it to five and buy the massager, it'll give some comfort, but I don't think you can do better than a good NHS physio to back it up. Excuse the pun!
