(a) looking at the GAMA style manuals, which appear now to be fairly ubiquitous, the AFM generally is embedded within, and is part of, the POH.
The regulatory required bits (ie the AFM pages) will be identified in a suitable manner, eg there might be a margin highlight that "This page is FAA-approved" or somesuch. These are the bits which are tied up with the certification and must be observed.
The non-regulatory bits comprise the remainder of the POH and represent OEM recommended practice and the like. Good gen but not with the force of the regulatory process.
the AFM generally is embedded within, and is part of, the POH.
Well, more no than yes. Whatever document it is will have been submitted to the authority for approval as a whole. In the standard format (though I have seen slight variations) it will contain: Section 1, Introduction, 2 Limitations, 3 Emergency procedures, 4 Normal procedures, 5 Performance, 6 Weight and Balance, and perhaps 7 Systems description, other sections as the manufacture may wish, then supplements. I have seen differing numbering when a "Abnormal Procedures" is included between EP and NP, but this is uncommon for light GA 'planes.
Accepting that Section 7 and after are optional, otherwise, the preceding sections will be required. Of those, Limitations, EP, NP, and Performance, will be approved, and perhaps identified as such somehow. In any case, the wording in those sections will not be there, unless the authority has agreed to it. The Limitations section will probably be presented as "mandatory", as it is the pilot's link back to the operating limitations expressed in the Type Certificate Data Sheet (TCDS), which is not commonly available to the pilot.
FM Supplements should follow the format of the FM, though I have seen drift on this. The information to be read on the first page or so, or beginning of the Introduction, should make this clear to the reader.
I'm always amused that there is always a limitation presented, which the pilot has no way of measuring - G loads. Other than referring to the angle of bank, unless a G meter is installed, the pilot cannot determine that they are remaining within the G limits. This is why there are maneuver limitations, and prohibition of spins and/or aerobatic maneuvers, so the pilot just should not get near those limits.