The show gives us glimpses of the afterlife, the interlife, the region between, or whatever the hell they call it.
"Heaven" doesn't resemble those Sunday School picture book illustrations. No golden streets, pearly gates, or angelic choirs hanging around on clouds and playing their harps.
In her interludes between death and rebirth, Prairie pops into a three dimensional X-Y-Z grid of light . This cordinate system divides the blackness of space. Tiny galaxies drift by at infinitesimal scale. (and furiously accelerated time scale too. A second = a million years, or thereabouts.) The galaxies float through Prairie and her Sprit guide. Which implies this is place is no place. It's more of a user interface. An inter dimensional operating system,.
Did the angels build this place or do they just work here? Who are they working for?
If there's somebody upstairs, they aren't mentioned.
This isn't so much a spiritual realm as a physical realm in higher dimensions. More like the wormhole timey-wimey subway system in Doctor Who, and It only looks like religion, folks. But it's really science. Quantum physics and the something universe theory.