This one is actually promising in blender, it´s setup for eevee though, which I rarely use, so I have to check if it converts well to Cycles.
Appending seem to not work for me, I might be doing something wrong…but I opened the blend file in blender 3,4 alpha, and it works.
The main node could use a bit more settings, if one goes in to the node and make a channel for some of it, like texture location, some detail control as well.
Addons I know too little about though, maybe there is the place you should look for larger cloudscapes.