I was honestly wondering if a bug had prevented any AI empires from spawning for the first 25 years of this game, but I found them eventually. Expanding as fast as my influence would allow in two directions, my Militarist Egalitarians looking forward to play with the Idyllic Bloom civic made first contact with 2 races almost simultaneously. One of which, arthropoids, boarded my science ship and summarily executed the crew.
So I was a little confused when I got contacted by the Fanatical Purifiers... But they were molluscs? All became clear when the arthropoid Devouring Swarm contacted me shortly after.
that went about as well as you'd think, especially since I hadn't invested in anchorages at all. I threw together a relatively high-tech fleet almost of almost 40 ships and tried to gank the Purifiers while the Swarm was busy devouring someone I hadn't met, but they countered with a fleet 50% stronger. Since I myself was 50% over my fleet capacity, I decided to concede. This is as militarist, mind you, but really it was just supremely bad luck. I was just as likely to roll pacifist authoritarians as neighbors, and I was largely to blame for overexpanding. (I also didn't remember "nonadaptive" would give me 70% habitability on worlds of my exact biome).
Gotta say though, the Idyllic Bloom thing doesn't seem very strong. Even the first stage (of four) costs 1350 energy, then 20 energy/month and a building slot, just to get +10% pop growth. And the planet type has to match your homeworld, and it takes like 14 months to build that stage. It might be a great flavor thing, but... if you're going to be terraforming anyway, there's a perfectly good ascension perk.
On the other hand while Idyllic Bloom doesn't work with Habitat or Ring World preference (or Life Seeded lul), it does appear to be compatible with Tomb World preference. And I do know one way to "terraform" to tomb worlds, though it takes a particular civic
Edit: (furthermore, budding seemed kinda nice but I was still struggling for pops to fill jobs. Probably shouldn't have expanded to non-tropical worlds as Unadaptive. Frankly I shouldn't have taken a wet world preference, but I was trying to play plants and maybe even take the *objectively waste of a pick* make-alloys-from-food civic eventually. All for flavor really.)