Hi @JLFRM2020 GARP's Part 1 notes (you may or may not realize) are new in the sense that it's the first year they wrote them in house; previously they were assigned to external authors, like Part 2 currently. My view is that new Chapters 4 and 5 are are pretty weak. The first Learning Outcome (preserved from last year when the reading was stronger) asks us to "Compare different types of credit derivatives, explain how each one transfers credit risk, and describe their advantages and disadvantages." and the text goes on to introduce products, "These included credit default swaps (CDSs), collateralized debt obligations (CDOs), and collateralized loan obligations (CLOs)." But unlike previous years, this first-version doesn't bother to illustrate any of those vehicles. I'm glad to maintain our quality and depth. (Their next version will gain the benefit of copious feedback ...). Normally, we might look to their EOC questions to answer your question, but GARP has taken a huge shortcut by writing EOC questions that are not representative; indeed, the Chapter 4 EOC include many questions that are far too trivial to be useful for actual exam prep.
So the key determinant here is (i) GARP's churn of the material and, again just my opinion, (ii) the shallowness of many of the new Part 1 readings (and I think Chapter 4 is one of the weaker chapters, although a persistent weakness of the new material is the lack of illustrated examples). In regard to your question, "How much of the notes is FYI vs absolutely necessary to pass the exam?" I can't really answer because GARP doesn't give EPPs much in the way of prospective (e.g., we have very few exam-type questions) and the exam is extremely over-assigned (always more material than can be possibly tested). Certainly, you do not need all of our notes to pass; our notes often go deeper and broader than required to the exam, some of it is due to the unpredictability, but admittedly must is due to the fact we care about mastery of the domain beyond the exam. I hope that's helpful,