I have no intuition for how hot or bright these trees would be. They certainly would be very different from the sun. The sun is literally incandescent; white-hot glowing. Trees would presumably use a mechanism comparable to glow-worms to generate radiation only in a very narrow frequency band. The fair skin color of elves suggests that they do not come from a high-UV environment.

Somewhat less than half of the sun's energy reaches us as visible light (43%). There are a few other factors that might allow the trees to glow brighter than the equatorial sun at noon. Unfortunately, the intensity per area diminishes with the square of the distance, so that doesn't get us far (no pun intended).

It would be much better if that world was basically rectangular (with reflective sides and top); basically a terrarium. That would also explain why you would place 2 light sources at 1 end. The length of a long rectangular box would only be limited by absorption of the light. The trees should glow brighter at the top. Plants, animals and structures on the surface, near the trees, are hit with only "mild" power, while the high-intensity light near the top of the box is absorbed or scattered by the atmosphere over a long distance. I'm not sure how to work out how long such a box might be. Mainly, I don't know what assumption to make about that high-intensity light at the top.

Anyway, we should consider that elvish anime eyes originally evolved as an adaption to low-light environments and only later became useful for seeing over long distances, because originally there possibly were no long distances.