Somewhat related to the topic ... I hope
Sometimes I'll create empires and throw them into a map with 1,00 stars and maxed empires/fallen/marauders, etc then go into observe mode with the game on the fastest setting and just watch what happens.
Some things I've noticed on this last one:
1) Machine empires that start with a machine world do not clear the last tile blocker giving them more replicator jobs.
2) Subsumed Will (the one that allows you to move pops with no influence cost) is not handled well by AI empires. Looking at a home world in perfect condition, has never been attacked and fully built only has 8 pops on it with 95 job openings at 2422 because the AI moved them all to other less productive worlds.
3) Habitats are still built but often never colonized with some AI, even ones that choose Voidborne as a perk.
4) Fallen and Awakened Empires do not take traditions or ascension perks. This may be by design though.
5) Not a single empire has taken Galactic Wonders, yet some took Arcology Project and never made any. This may also be by design, with the AI's current economy management I think they'd struggle to build a galactic wonder.
6) AI empires that chose World Shaper have never made a Gaia world that I've seen, even though they are often at or close to energy cap. Meanwhile empires that picked Hive World have made a few.
7) In an earlier run an Empire with Idyllic Bloom never made a single Gaia Seeder.
8) I've never seen a single Life-Seeded AI empire last very long. Although to be honest this is a really tough one, especially if you run into an angry neighbor early on, so no surprise really.