Thanks for the kind words about the book. As a general concept what was stated in the book about ordered vs. inline layers in regards to policy evaluation performance is correct, but probably requires some further context given your query.
Most organizations will start with ordered layers because they upgraded from R77.30 (or earlier) into R80+ management, ordered layers are essentially how things were done in R77.30 and earlier, and that behavior is preserved across the upgrade. While there are some extra policy evaluation optimization opportunities using inline layers as opposed to ordered layers, the performance gains that can be achieved are minimal due to the new Column-based matching paradigm which is used with both ordered and inline layers. So in my opinion the effort to convert an existing policy from ordered to inline layers solely for the purpose of gateway performance enhancement is not worth the limited gains.
Now if you're creating a new policy package for a brand new gateway, or a completely new Check Point implementation starting at R80.10+, inline layers are definitely the way to go. Inline layers streamline management and make policy editing tasks easier and less time-consuming for an administrator; please see this post from Tomer Sole which states the above to some degree, and corroborates what I saw in my lab environment when doing research for the second edition of my book:
https://community.checkpoint.com/message/9675-re-unified-policy-from-a-upgraded-r7730?commentID=9675...
How will layers impact policy performance?
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