It’s way to hard to generalize the concept without pushing science or religion. They can pertain to an outer worldly existence or simply just our multiple levels of consciousness. The energy body is a reference to the frequency lining the outside and inner of the body. Basically based off of frequency theory.
Also way to generalized. Many people believe many different things. In my experience - The higher self is the state of thought where you find serenity and acceptance in yourself and the world you are placed in at this time. Set and setting.
Practice. Also I can’t generalize it because everyone has different experiences. That’s the issue with the subjective nature of the metaphysical to begin with. You can definitely have shared similarities but I can’t tell you if it’s the same for everyone. In my experience, I have felt a shift in my own energy when working with specific entities. Mostly from confusion and not being aware of my surrounding self. I usually do my rituals blindfolded. You can also definitely experience these feelings after rituals as well by focusing on them. The human brain is like a machine that is always running and you can definitely control your present state with previous states that you have felt with practice.
There’s honestly no true answer to this as far as I know as well. The problem with magick is when you try to generalize it to something outside of yourself.