Hello, friend. What a great question! You know, I have been working in energy work for 2 1/2 years, and I have noticed that all modalities use the same life force energy for healing and all other applications. It is all the same energy that fills us, is in and around us, that makes us alive. Reiki, Pranic healing, Healing Touch, etc... these are all focus tools, systems, for using this universal energy. There are many energy systems in the bodies (spirit, emotional, physical), and they all flow with the same energy. The different modalities exist because we as beings of light LOVE our tools! Haha! In my owm practice, I have noticed that labels are handles by which we make exoteric ideas tangible. Reiki meaning 'rei', or god consciousness, and 'ki', meaning life force energy, is one label we use for the universal energy phenomenon. I was working with this energy for a very long time, even before I consciously knew it existed or had a name for it... Reiki is rhe focus tool I chose to make me conscious of what I was already doing. And I have come to realise we are all capable of this work. I have helped people feel the energy flowing from their own hands during guided meditation. I did not attune them to Reiki, but the energy was there anyway. All it took was me helping them FOCUS consciously on what was already there.
Anyway, I hope this answer helps. Perhaps it is not a treatise on the difference between the various tools. It is just a bit of my personal journey...
Many blessings, friend.