Angels are spirits that can take on many forms in the physical plane. Some people believe angels are direct extensions of God, but most people believe angels are spirit entities who are Heavenites of a higher order than souls, and most people believe they have a good bond with us both here and on the other side.
Angels can appear in the physical plane as winged humanoids––just as we often think of them––but only in ghost form. In ghost form angels can take any possible form; they can be dragons, aliens, fairies, leprechauns––whatever God wishes to design for them.
I’ve only seen 3 angels personally. All 3 were orb apparitions. This is perhaps the most common form that angels take in the physical plane. Orb apparitions can be small or they can be large; they can be numerous or they can be singular. Orb apparitions also present in different colors. The first time I saw an angel, I was in my bedroom reading about the afterlife. The apparition presented before me as a luminous shower of blue crystylic pellet sized orbs, and it made feel physically warm to be in its presence. The second time it was the same exact thing. Blue crystylic beads once again. The third time I saw an angel, I was sitting on my patio, and 50 feet in front of me I saw for about 3 seconds a giant white orb; it was between the size of a beach ball and a soccer ball. A very dense apparition. It was pretty amazing.
Garden Path 
It’s all pretty well explained in the neurons and hormones. These visions are common in the lab when stimulating certain portions of the brain—Projections from self. They also use this information to help people reposition their phantom limbs and ease pain by projecting the correct image of the missing limb in a mirror and tricking your mind. Fascinating stuff. Angels? Hardly.
We also see shadow people and Outer body experiences in the same research. It’s been proven it’s a projection of self when the left or right brain speak to itself. A little crossing of the wires and poof! Angels. The brain is a complex tool that misfires from time to time.
Your facts are inaccurate. It has been demonstrated in labs that acute stimulation of the left temporoparietal junction of the brain can generate hallucinations of shadow people, but not ghosts, not orbs, not angels. Also, hallucinational shadow people generated by stimulation of the TPJ are very different than apparitional shadow people. The two are not the same by any argument that I can obey. Please read this post I wrote, called My Opinion > Your MD, for a complete answer on this precise issue.
https://lukeymeyer.com/2019/11/17/my-opinion-your-md/