Welcome to the forums. When working on something like this in a global perspective, try to think about how each layer of clouds works individually. Maybe play around with getting familiar with the cloud fractal settings and cloud settings.
nvseal's presets seem to be pretty rough to my eye but it seems to possibly be 3 layers, low level (small noisy clouds) mid level large clouds, and high level thin clouds.
Have a look at this example file. I'm not positive if the preview I saved is from that working file exactly (there are iterations) but more or less should be the same.