i forgot a detail, in the top, behind the MESA mountain, i fullfill with Dark Sea Blue...

i tell you cause i say on last step i desaturated blue... i mean this blue sea as i put there as Sky. and then turn into grey

this is the @Quenten image that inspired me make this "style" :D

On the lightroom i use mainly contrast, overall color saturation, clarity.

as i desaturate the Blue, the color becomes "grey" and using strong dark vignetting this grey becomes "night".

after i think in a moon... just create 2 circular/radial filter and push exposure to extreme. the first one bigger and more difuse intentisy on the borders, and another inside - smaller and more intense on his end - to emulate a moon and his aurea.

hope i can help

once again i normally adjust mountain size by eye.

at this point i finished the image on light room and export a png to work on colors in lightroom (as a photographer this program is very easy to me). But also you can enhance the colors in this tutorial from @Loopysue on https://rpgmaps.profantasy.com/shore-and-ocean-effects-for-overland-maps-part-1-edge-striping/

i just feel myself more confortable using lightroom as a very long user.