as i understand the information that we have so far, the angleans are raiders: that's how they interact with the outside world primarily. other factions dont really like them, and they are a threat to everyone, but they aren't going to INVADE. They dont want more territory, they want your stuff! the angleans i think was said in one fo the pax videos are technologically advanced, but resource poor. this explains why they have to keep raiding: they need more metals and food and feul and bullets and stuff, or their whole society is going down the tubes (haha get it because they all live underground!) the angleans are primarily subterranian dwellers living in the ruins of the old world, they have used those ruins to develop seriously advanced tech.
as for government, they are a republic, that means they have representatives who assemble to vote on laws and such. it might be elected representatives, or heads of clans, or whatever! republics might have some kind of executive branch, king, prime minister, president, consul etc.
hyper teched, resource poor. i'd imagine they might have some trade or interaction of some kind with the chaledonians, wo are natural resource rich