How to make such volumetric clouds

I want to make a game whose events will take place above the clouds, but the clouds themselves must be voluminous so that they can be flown through, they must also completely cover the earth, in other words, clouds to some extent must fulfill the role of landscape. They should also be a kind of multi-layered, that is, the upper layer is always light, and the lower layers are darker from a smaller amount of light. I tried to do this using Volumetric clouds, but it constantly turned out not what I wanted. There was an idea to manually simulate clouds, but it looked too complicated. I took this screenshot from the video to demonstrate what I want to do approximately. I also had the idea to use Landscape, but I don’t even know how to make a cloud out of it.