I just wanted to chime in on the performance thing and on commenting on the design change and how I see it. Sorry for the tangent. I don't think research numbers are being touched but each type split up more explicitly so you can literally focus more on a particular area?
In the simplest terms, you are going from having an instance of an object for every pop (thousands) which isn't a huge amount on its own but convoluted with how many checks, triggers, there are probably hundreds of if()'s within the pop growth/addition areas. And they enact on day 30, day 1 or just whenever a trigger defines it too. And you're meant to do that on a infinite loop. And I think because the addition of larger galaxies wasn't in the games release, it likely wasn't seen as a flaw and a nice function of the game to represent each pop quite literally.
What they've opted for is simply having as many pop objects as there are distinct versions of them (now groups of the same pop) and calculate those groups. They'll have simplified their code some and rather than creating a new object every time a Pacifist is murdered or birthed, they will be adding / removing from their existing group a 1 or 100. It won't be exactly like that but you get the jist.
Does a Thegian Pacifist with Fanatic Spiritualist exist in the galaxy? No? Create a new object group and give it 100 or 1. Yes? Add +100 or +1 to the existing group.
Much better than just creating more pop objects and having to check every single one. I still want my pops represented individual though and for that reason I'd add lots of properties to what is a pop group so that its possible to have very granular pops of the same species.
The fractional part will come into representing each empire with a slice of those numbers from the whole of the galaxy. And then using those numbers to create the groups.
On the face of it, HFY is right, it might be possible to get as many pop groups as individual pops but the sheer calculation requirements will be much less onerous. And it'll be mainly because of shifting calculations to on groups than every single pop. This is bringing in simplification whilst bringing on board Estates and Houses or whatever it's called in EU4(Johan!) as well as leaving room for an explicit Spiritualist axis of religions which I really hope will happen. Also don't forget, this empowers the team to reign in on what constitutes a pop group too.
I'm pretty hopeful we'll see some good change for my Huge galaxies on my 10100 CPU. Whether you see this game reaching its golden years, its facing its biggest critics head on. I just hope we don't compromise on gameplay and how pops feel prior to 4.0.