Whether it is called a; Style Guide, Documentation, Overview, etc., they all refer to some specifics of what is being used--which is what you were asking about. The thing is to "know" HTML5 so you can spot inconsistencies or errors whenever you see them and/or add code where you see fit.
As to what template you should "stick with" or use, it should be according to your needs. If it is correctly coded and you can use it start with it, then adapting it to your needs is a lot easier.
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