Super anecdotal response here.
My son did neurofeedback locally at Family Compass in Reston. It is so hard to say exactly what helped my child because our interventions were multi-pronged. The research I did shows that it is especially helpful with PTSD and maybe generally with anxiety. My son had generalized anxiety, ADHD, a severe learning difference but I was only hoping it would help with the anxiety. We tried it with a kind of all-we-lose-is-time-and-money attitude. My son enjoyed the sessions and there is no question he made huge improvements over the years he was doing neurofeedback. He really struggled as a young child - like can't leave the house/not sure what his future would look like - and is now a confident college student. But again, we were doing many other interventions at the same time.
I want to add that I decided to try it at the same time. I didn't do it for as long as my son, only for a few months. My experience was that I felt tremendously calm and grounded for the next 24 hours or so. I would try to explain to my husband and he'd ask, "was it like you had a great massage?" or "or like you did yoga?" But it was not so much relaxing for me as centering. Like everything was sharp and in focus but calm.
I know that is not a very scientific answer. I am the least woo-woo person on earth and, to be honest, I was skeptical the entire time. I felt like it was one tool in the toolbox and I was happy we used it.