It all depends on the style. I saw perhaps 3/4ths of the video, will finish it later, and the key elements are great, but you need to apply it to what you like most, I suppose. These aquariums look diorama-ish to me. Impressive, but not what I'd do, if I had 1/10th of these people's ability. I always look at the Biotope Aquarium Design layouts, those are AMAZING and what I aim for.
As for the branches, I usually see the "thin" parts of the wood on the top while looking at wood in the river. Trees are uprooted and fall into the stream, and really interesting spots get formed at the root structures that remain half in, half out of the water. They are in the shallows, so this is usually where a fish you can keep in an aquarium would be. They provide refuge, and their structure usually provides places for mosses and aquatic plants to grow, as well as riparian plants to emerge. Aquarium designers very often do triangular scapes with root like structures going down, which in my experience usually does not happen with trees, only perhaps with shrubs and softer plant root structures.
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