The alternate endings are much easier on easier difficulties. ESPECIALLY Fallen Spire or Ancient Shadows. If you're just looking to see the content, don't do 7/7, you'll have enough problems with the 120 planet maps you'll need to get at the AS stuff.
The opening crawl for AI War mentions that the humans still have some loyal AI subroutines, all the turrets and (probably) most of the fleetcraft are automated. Not sure about that though since Mercenaries are a thing, unless they're selling you the tech.
Alien races are an interesting case since they're all a living ship of some kind. Neinzul are the most obvious, but Zenith vessels are Zenith entities, and Spire tech crosses over with Spire biology in more than a few places. We know they're alive, but whether they're piloted...