Best way to design clear to cloudy system?

Yes, sorry it’s not very exciting, but it really depends on what your targets are. I’m assuming that’s focused on the gameplay, so there’s no need to re-invent the wheel in other areas, especially where it’s already been done really well…

As an aside, I do know that the process is basically to do with applying noise textures and / or photos of cloud textures to a large sphere. So, no actual cloud objects in the sky ( they would have to be way too big to be practical ).