You are covering a lot of subject areas in one post. Let's start with the primary question - can you use cedar granules for pests in bonsai soil?
Even that question is a little complicated. "Pests" in soil are usually uncommon. In fact, healthy bonsai soil should be "alive" with micro flora and fauna. I regularly get mushrooms and moss sprouting in my pots - which is typically the sign of a healthy environment. So I wouldn't necessarily use cedar granules to control "pests". However, there is nothing wrong using cedar chips as an organic soil component - if and when you need an organic soil component.
Some of your other points touch on the art of bonsai - and what it is versus what it isn't. Bonsai is about evoking a sense of nature in a small enclosed space. You want your tree in a pot to look like an old tree in nature. Yes, you have some artistic license to style in some movement or otherwise make the tree a little less "natural" looking, but braiding trunks would look glaringly unnatural - at least as bonsai. What you are describing would be a topiary - something you would find in a formal garden, where trees are styled and pruned to take on geometric shapes or look like animals, etc. Both are art forms using trees - but the goals and results are quite different.
I wouldn't say silver maples are "bad" bonsai material - but they are challenging. However I think if you are raising your trees from seed, you could overlook some of the challenges because the trees have an emotional connection to you. Try looking at photos of old silver maples in nature, find a photo you like, and then create a plan for how to grow your tree to fit the photo. And enjoy the journey!
