Is there anything that wasn't said in the video that I need to know in order to build this from scratch
patdoc I would say as long as you know about the benefits of backface culling, object data properties (and the ability to toggle off objects’ camera property but allow them to catch shadows, basic compositing and denoising, and perhaps a little bit about llighting then you should be able to do this from scratch.
One benefit of having this example is opening it up and learning from the things that were built. You can also use it as a template from which to start other projects.