The first FMJ amp - the A22 - was electrically identical to an Alpha 10 but in a new aluminium casing.
The DiVA A85 and FMJ A32 were almost electrically identical to each other. The A32 replaced the A22.
It is worth noting the A85 and A32 underwent substantial running production changes during their lifespan. The early amps had BFA connectors and did not employ current limiting on the output stages, so had enormous dynamic reserves all the way down to a 1ohm load.
The later A85 and A32s had banana plug connectors, and did employ current limiting. There were some other internal tweaks, to hardware and firmware. It is interesting that reviewers of the original A85 and A32 call them 'dynamic', 'fast', and 'engaging', whilst reviewers of the late-production A32 call it 'boring'. One wonders how much of the difference in reviews is attributable to changes in running production.
The FMJ 'label' was eventually extended to almost the entire product line, having previously been reserved for the top-of-the-line models. It was then mothballed and Arcam now produce kit that I am largely not interested in.
I haven't tried the Class G kit and I probably never will.
I have owned many, many bits of kit, including many bits of Arcam kit. Probably the best sounding amp they produced, IMO, was the early production A32, which was very close to being the perfect amplifier.