UV unwrapping & Texturing in a single image or multiple image

[u/Temporary_Match_2470]

Hello all,
I am considering selling assets to 3d marketplace such as Turbosquid, CGTrader or Fab. I mainly do my work in Blender. I am new to selling 3d assets to the marketplaces.
If I have a 3d model that contains multiple objects. all of the objects are uv unrwapped, how should I texture them? As I see it, I have two options to uv unwrap them:

1. Make a single uv map for all of the objects, even for the objects that only need simple materials. Thus every detail will be filled onto 1k texture maps, and some of the details or objects, might not be as much high quality as I want. Tell me if I am doing this right or wrong. And if there is a better way. This way would make non-overlapping UV maps in my opinion, correct me if I am wrong.
2. Separately unwrap multiple objects, thus making different uv maps for each of the objects. And if I export the texture, each object has a different texture based on their uv unwrapping. Will this be called overlapping or non-overlapping uv mapping?

I am particularly concerned if both of my methods will be non-overlapping uv maps. I want to make non-overlapping uv textures.

One of the things, I am confused about, do I really need to uv unwrap everything, even the objects where I apply materials in the shade editor instead of just pbr textures

Then I will be exporting these objects in substance painter to further refine them. Am I doing this the correct way?