DM Bears:
But what about two overlapping magical lightsources? For example, if you cast Moonbeam on top of a Dancing Light orb, which wins out? Higher level? Order of casting?
Actually, the spell "Darkness" offers a bit of potential insight on that.
Darkness:
Magical darkness spreads from a point you choose within range to fill a 15-foot radius Sphere for the Duration. The darkness spreads around corners. A creature with Darkvision can't see through this darkness, and nonmagical light can't illuminate it.
If any of this spell's area overlaps with an area of light created by a spell of 2nd Level or lower, the spell that created the light is dispelled.
"Darkness" itself is a 2nd level spell. While magical light will illuminate it, any light-creating spell of equal or lesser level that crosses into the 15' radius of magical darkness is dispelled/snuffed out. For example, Mallory's "Continual Flame" lantern (a 2nd level spell effect) could shed bright and dim light into the area since it has such a big radius of effect, but if the lantern actually entered that 15' radius it would be snuffed out until it left again.
So this element means light-producing magic of a higher level than "Darkness" would overpower its light-snuffing nature. We could reasonably extrapolate that outward and say that spell effects that directly counter one another are prioritized by level, unless the spell text specifically states otherwise.
DM Bears:
Also, Khulekani is up. Do you feel like posting? I'll certainly say that you guys on the Astral Plane know that something is amiss by now. Not only can you glean the action, the pillar of Moonlight and Astre's appearance would do more than enough to clue you in that a fight is going down. What I'm saying is that if you so desire, it's time to jump into the fray.
Worth mentioning, in case folk didn't quite realize, but sound carries through the entryway into the "Rope Trick" space. Since everything going on is pretty nearby, it's likely everyone can clearly hear what's going on with the battle outside since nobody out there is trying to be quiet.