I know and have known a number of Reiki masters..and folks at various levels of training and atonement (at-one-ment).
Reiki has two main forms as I know it, an Indian version and a Japanese one. It is quite systematic, dogmatic, steeped in tradition.
My belief, like religions, all the hands on/off healing techniques come from the same source and utilize the same source energy.
So whether it it Tui na, Jo rhe, Reiki, Ki gong, or even healing touch (the US nurses sanctified method of energy work) it is utilizing love and G!d as the energy and a practioner as the conduit.
As for efficacy, I'm a participant and have seen some incredible stuff. But I'd still go to an allopathic MD to get a broken bone set...I may go to energy work or accupuncture afterword for pain management and additional healing...
I've never been formally trained in anything, but I've had good results with animals and people in energy work. Mostly it seems to help to relieve pain and speed healing, particularly through reducing inflammation and infection. Outside of acute trauma, most of my animals also live years past their "expiration date" in terms of average breed lifespan and also in terms of chronic illness without treatment. My cat, for example, lived four years past her expected lifespan after being diagnosed with advanced kidney disease, and I did nothing but continue to give good food and love, along with energy work. Many veterinarians have remarked that my animals are exceptionally youthful and healthy. I believe it is a combination of good care (quality food and clean water) and love. I've never sunk a lot of money into any special treatments or supplements or anything. But I do spend a lot of time with them simply loving them, and I do energy work, particularly if they injure themselves in any way. I've thought about getting some training in Reiki or other energy work, but so far winging it seems to work fine.