You do not made any confusion. The FG in the new design it is just a marker, and as I recall was 7 kind and was no error, was design as we find. The
Wide AM come from lowering the relief in order that the Dies can strike more coins without damages and was design more for proof production. Was use in Denver and Philadelphia a few years Intermittent.
If you want more technical detail I can post but for "gold" coins variations peoples it is not so interesting.