Ok so here's how my empire look like.
At the beginning I wanted to make an divine imperial government, turn enemies and friends into tons of vassals, sort of like imperial japan, but then I saw this civic "exalted priesthood" and I though that a caste of priests leading it's people in galactical conquest in the distant future is interesting and quite new concept for a science-fiction. I had to switch to oligarchy though, but that's okay.
I'm in late game now, most of the empires are either destroyed or vassalized. Currently the biggest fish in the pond is Pellisimus Galactic Hierarchy. They are very militaristic and xenophile so they are very powerful and a clusterfuck of various conquered races. They managed to beat the end-game crisis alone, no help from others, and in a very quick time. Technologically they are at my level, but in fleet power they are about half stronger then me.
Next is me, yellow on the map. Furry foxes are the most common race, but I have a few of others, some from conquered nations and some from uplifted species. Actually those uplifted guys are my ground soldiers as they are genetically fitted for psychical strenght while my main race is focused on research and leadership. Usually I gradually grant full rights to citizens of every species, except for one race that used to genocide my planets, those fuckers gets expelled. I managed to beat one fallen empire alone and get their super-advanced planets and also I'm first in the galaxy to start building megastructures.
Sactro something something union is the 3rd biggest empire. They're inferior to me but still respectable in strenght. We share spiritual values so they always have been good friends for me. Nothing much to say about them tbh.
Yibrak Mercantile guilds used to be quite small for the most game, but in one moment in the game they colonized twice the amount of planets they had moments before, by grabbing planets I had interest in while I was attending other matters. Also lately they decided that they hate me, closed borders, no trade etc. and their power is pathetic. If it weren't for their defensice pacts with others I would erase them already.
There also used to be 4th big empire which was quite powerfull and also my rival, but they got rekt fast by Pellisimus. Their remaining worlds begged me to become my vassals and I happily accepted.
The rest you see on map is completely irrelevant, either my or someone's else vassals. Of course there used to be much more empries but they got rekt by me and 2 other big dudes. I ususally preferred to liberate planets and turn them into gazilions of vassal states.
Now I don't know what to do next. I can't start the war with the biggest guy because he's more powerful, and we all had defensive pacts with each others. Recently the other empires stopped being friends with the biggest guy so there's a chance for me to beat him alone, but he's still stronger so currently I focus on technological advancement, colonization of new worlds and building economy.