All of what you showed as reference is a very surreal art style. I don’t think “just” creating some lightmap and turning on glow will do it here for you.
It’s starts with a consistent and outstanding look of your 3D models. So using standard Asset packs will most probably not bring you the wanted results.
Then I think the one magic trick you are not expecting is shaders. Especially the light part in it will most probably change the appeal of your scene a lot. Standard BSDF Shader (that is used by default for every 3D objects) is designed to replicate reality. However you don’t want to replicate reality, you want to replicate a painting.
This video gives a great overview of what is possible when creating your own shader: youtu.be/jlKNOirh66E
It uses Unity but at least in theory I think you should be able to recreate all of this in Godot.
godotshaders.com holds some impressive shaders you can use and expand on.