The Burnished Plane

Also known as The World, as the plane itself is conscious. This consciousness is contained within its true body, a massive 22-headed Phoenix Kaiju that lives at the heart of the infinite(?) fire that spans the primary level (or "floor") of the plane.
The World's initial personality is curious, creative, incredibly patient, lazy, and detail-oriented. It has a mind that is shaped ready for the long wait of eternity - it is an alien being capable of waiting centuries without feeling displeased. It has access to an endless font of inspiration; it will automatically get new ideas if it sits idle for too long. It has a great deal of creative - and literal - control over the plane.
The World can also split its mind into subprocesses, to manage local projects. However, it has many smaller avatars throughout the plane that will do most of the interacting.
If the true body of the World is slain, it will be reborn in 24 hours with a new personality (but the same abilities) as a baby new World (sort of like a hard factory reset).

Anyone who dies in the Plane of Light doesn't die permanently. Rather, they have a choice:

deny death and be reborn as they are, but after a time. First death 1 year, but after that multiply it by 5 per death. During that time in stasis, the World has access to their memories, thoughts, etc

accept death and be reborn in a random new body back on the material plane. The body is a random age younger than their current age, and a random species. They also are reborn in a random place, within 1 mile of a settlement. There is a very rare (1 in 1000) chance of the creature being reborn in a special body designed by the World. New body form must be balanced to Players Handbook Standards, lifespan between 50 and 500 years, and when reproduces, only produces a child of the other partner's species. Rebirth erases memories, except for dreams and deja-vu type of stuff

The Pinnacle

A spire of light that shoots directly up from The World's true body. This light is encircled by an infinite number of rings, each as large as The World decides they need to be. Each ring is connected by something that allows for some form of transportation - this could be, for example, a river, staircase, or elevator. Although the rings are infinite, it somehow takes only 21 trips to go from the top to the bottom (and vice versa). The World's creations found here cannot leave this Plane for long without slowly losing power and light, and will return back to the Plane after several days. These top and bottom rings have been set by The Phoenix Queen and can not be changed by the World.

The Ring of Memory

The highest ring. Its landscape is littered with lost cultures, lost cities, and monuments to antiquated or out-of-vogue concepts once found on the material plane. The land itself mimics the scenery material plane, although exaggerated and more akin to artistic landscapes. The Brass Palace is located here.

The Garden of the Sun

The lowest ring. A garden of paradise where pain is dulled, food is plentiful and delicious, and drink abounds. At its center is a humanoid avatar of The World; indestructible, made of pure light, and unable to leave.
This ring also houses The Tree of Life and its Angels. The Tree of Life, made of glass and lightning, bears fruit that looks similar to apples made of liquid fire. These fruits, when consumed, will restore a person to adulthood if they are older. These fruits grow slowly and slowly lose power when they are removed from the plane.
Should someone eat 22 of these fruits or pledge themself to defend the Garden, they will become an Angel - a being of metal, flame, and light similar in size and shape to their original form but with silver skin and wings of flame. Angels sleep in the garden in crystalline pods, but can be awoken by The World at will. Angels are unable to leave this plane except when magically summoned, which would require powerful magic and be very temporary.

The Rings of Struggle

Pain is reduced to discomfort on these Rings - which are much more dangerous and loot-filled than the others - and littered with tests and trials for adventurers. Items removed from the Plane retain their power for much longer than other items from the Plane.
These Rings also contain Heroic Edifices - dungeons where The World plays Dungeon Master. At the heart of these dungeons are Heroic Vaults, which generate personalized powerful magic items to the desires, aesthetic tastes, and whims of each adventurer who makes it there. These items, when removed from the Plane, permanently retain their magic.

The Maelstrom

Surrounding The Pinnacle and its Rings is a powerful wind tunnel of air and melted reality blasted upwards from the fire below. Reality within the Maelstrom is dangerous, bendy, and messy - it can be shaped by mortal will, but can quickly become uncontrolled if the traveler is unfocused. Negative emotions felt here can manifest as physical dangers.

The Spark Void

The Blackness surrounding the Pinnacle, where Winged Suns flutter around. These are tiny suns, with bird wings! Winged suns range from 100 feet in diameter to 2.5 miles, and they have their own tiny solar systems that grow to orbit them. At the heart of each sun is a miniature version of the World's true body (just a lesser avatar).