I would define AGW as proto-ambient, with a foot in the Progressive camp (most of the musiicans were from that genre). Completely agree that it's a perfect album. Could argue there is some inspiration from the Harmonia album that came out a year before, which Eno effusively praised. After AGW, he would produce an album with them.

But Eno's 4 non-ambient albums in the 1970s are all classics and each so distinct in their own style.