I have attached a sample picture from Matkovski Dragos' project "Illustrat3d Nature". I looked up for the workflow to create clouds like these, but I didn't have any luck with that. The only thing Dragos mentions about the clouds is that they are created using a particle system to create infinite variation.
I am assuming we use emitter particle system to create these, but I am relatively new to this topic so I could be wrong.
Any help is greatly appreciated. Thanks!
[I am using Eevee rendering engine]
Edit:
Added my shader setups for world and volumetric fog.