congratulations on this find! AWGSes are a neat peek into Apple's corporate psyche in the '90s -- one component of a bigger picture of "we need to build everything any mac user might want" and a part of that was servers. They were mostly aimed at workgroups/departmental usage or being aimed at specific tasks.
AWGSes are uncommon compared to their "desktop" macs but for the most part, they're identical.
The 8550 is, as far as I know, the third time an AWGS differed from the base machine.
- AWGS95 (only model ever to ship with A/UX, had the PDS cache/scsi card available, otherwise identical to the Quadra 950)
- AWGS9150 (there was no PowerMac 9100)
- AWGS8550 -- if I remember right, these don't share the 8500's A/V ports, however the underlying circuitry is there on the motherboard. (I was actually surprised when I discovered this, it was like... under 2-3 years ago.)
(user-configurable specs can also differ, some AWGSes had higher base RAM allocations or bigger base disks.)
There was a rumor long ago that the AWGS either 60 or 6150 had better SCSI but as far as I know, that has never been substantiated.
W/re the software: up through to the 7250/7350/9650 in 1997, the AWGSes had a few different software bundles available. Sometimes they included AppleShare, sometimes it was the same base system 7 load-out the desktops had, the idea being that you would install your own server software on it, whatever that happened to be. (And there was plenty of different options for all sorts of different tasks.)
As far as I know, the Beige PowerMac G3 AWGS is the first generation where the base software loadout included appleshare on all shipped examples. (At least until Apple started bundling them with Mac OS X Server.)
The other half of "there aren't that many AWGSes" is that lots of people bought non-AWGS Macs to do their services. My PowerMac 7300, as just one example, came from a regional CLEC telco/ISP and had worked as a mail server, but it's a regular 7300, not a 7350.
EDIT: found my older notes --
https://doku.stenoweb.net/doku.php?id=macdex:awgs-software-loadouts
Apple's own magazine (which you used to be able to view on vectronics apple world) talked about the different bundles you could get with the 7350/9650.