The overlays would go on the bottom for a PC game & the top for a mobile game. The lion kingdom discovered despite the boom in mobile gaming 5 years ago, most gaming is still done on a PC.
This exercise revealed how Godot renders the glyphs in a fixed point size & then scales the output instead of scaling the point size. It looks so awful, all text really needs to be in a separate layer from the graphics, with a manually scaled point size to look good.
An interesting video surfaced of convincing graphics in Kerbal space program. The only environment map is the stars. Godot uses the environment map to draw reflective surfaces, so that wouldn't work on the ground. They use a 2D plane for clouds. The planet is a very large mesh with levels of detail. The atmosphere could be a 2D texture behind the planet. They use particles for some clouds. They use a fog effect, but only on the planet. Godot can't apply fog to just a planet. Lions don't want to port the entire scatterer library.
The lion kingdom has realized without seriously cutting down the graphics, nothing is ever going to happen & the growing amount of investment will be wasted. So it sometimes feels like a toy project with an indefinite finish date, decades in the future & sometimes feels like a disaster.