well, clouds are 5000m tall
density 0.2
edge sharpness 3
The key to get the right cloud profile is in reducing the coverage gamma, though, so that the point from which clouds begin to "grow" is pulled down.
The fractal feature/lead-in/smallest scales = 5000/15000/20
Perlin Billows
upped buoyancy
no warping
That's pretty much it. It helps with the lighting to blend by a distance shader so that before and behind your main cloud, the sky remains empty.
Cheers,
Frank