The cloud example you see in that video was created with just a single cloud layer, but it does indeed use lots of blue (function) nodes, numerous density fractals blended together, and it results in a fairly complex and demanding (to render) setup. Adjusting settings of this setup is quite challenging without an existing and thorough understanding of Terragen noise functions. Anyone deeply familiar with both the shapes generated by Terragen's noise functions, and the shapes represented in real-world clouds, could (with sufficient math/function knowledge) create something similar, all the building blocks are there in Terragen already. So basically, if you had this example you might be able to make the exact same cloud, but it would be hard to make variations of it that look more specifically like what you want unless you had the knowledge that would have allowed you to create it in the first place.
Given the complexity of that kind of setup, what we're trying to do now is encapsulate that quality of output into easier to use "preset" kind of nodes like Easy Clouds. You might for example see a "thundercloud" or "hero cloud" option in the future which would give you something like what is shown in the video, but would be much more easily controlled. It would not be as flexible as the pure raw nodes setup, but that is the inevitable trade-off: ease of use vs. flexibility. If you just want to achieve cloud types like that one, then we can hopefully provide you a solution in the future with more Easy Cloud types. If you want to know how to create the specific shapes you want and achieve similar realism and quality to what is in the video, then you need to focus on really understanding how Terragen's noise functions work and how to blend them in 3D space to get a specific outcome.