Yes, the Light of the Two
Trees Physically and Spiritually (Mentally) changed people.
The "Light" of the Two Trees was different from the light (small-l) from, say, a Candle.
And within Eä, there were metaphysical properties that existed, otherwise, which would give the "Light" the ability to both physically and mentally/spiritually change people.
Associated with "Light" within
Tolkien's work is "Good" (not just "good," but "
Good," with a Capital-G), and "Darkness" with "
Evil" (also, not,
Capitals).
This is because within Eä, "Light/Dark," and "Good/Evil" where things that existed as both pure Platonic forms, but also as Physical things you could touch, put in your pocket, make bread out of, or... indeed.... Make a
Magic Ring with.
And those
Elves who lived in
Aman were exposed to this
Light, and thus changed by it, due to something else that is true within Eä: Physiognomy: That the spirit or soul affects the appearance of the body.
The
Light of the Two Trees affected
both the Hröa and Fëa of the Elves. It gave them a power that appeared as light (small-l) to others who saw them, and as a Light to those who were perceptive of the Fëa or Spirit.
This is why the
Sindarin were called the "
Grey Elves," in fact.... Because
Elwë Singollo (and in the earlier accounts, many of his kinsman) had been to
Valinor, and been exposed to the Light of the Trees, when they remained in the darkness of
Middle-earth, they brought some of that Light with them, but not as fully as those generations who had spent centuries or millennia beneath the Light of the Trees.
This is an aspect of Middle-earth that Tolkien was really anxious to fully give an account of, but he ultimately failed because he did not have a deep enough understanding of the Hard Sciences to know what was needed for a full Metaphysical Foundation for
Arda/Middle-earth. But he did provide enough evidence that one could be discovered by those who did understand the Hard Sciences well enough to be able to tell what must be True about Eä, Arda, and Middle-earth in order for the world to appear as it does, and for the things within it to behave as they do.
And "Light" behaving differently than "light" happens to be a part of Middle-earth that is very easily explained without the need of metaphor or allegory.
And that explanation itself fills in other blanks regarding Middle-earth as well, and why certain things happen, why certain characters of beings can do certain things, why certain
places seem as they do, or why all of the previous even exist to begin with.
Most people who study Middle-earth tend to focus upon either the
Languages (and their creation, or similarity to Terrestrial Languages), or the
Peoples of Middle-earth (and their relationship to our worlds).
But when you begin as a Scientist, and you discover that Tolkien himself sought to discover a workable, or Operational Metaphysics for Middle-earth.... Then that is where you tend to focus, and it tends to be easier to discover such a Foundation than it is in our world or Universe.
MB