How to use a single texture for multiple game objects?

I wanna to keep the amout of the textures as least as possible in my low poly games. So I need to batch different game objects into one single texture,just like the asset linked below in Asset store

https://assetstore.unity.com/packages/3d/environments/historic/rome-pack-stylized-low-poly-151874


I want to know the work flow of the model and material asset . What kind of 3d tool is the most suitable ? Blender?Maya? Or some else? And is there any Tutorial video for this?

 

Ps ： For example in this texture, it looks like "color pallete" and " painting texture " shared in one single texture

 

I think most 3d packages can bake multiple textures into one textures and assign the new textures to the objects afterwards.

I'm not sure if you would need to join all the geometry into a single mesh before baking and the detach them afterwards of if it does it automatically. It might depend on you software selection.