What are you specs? If the race selection screen is "very slow" that would be the first thing I'd look at, as this should not be taxing your PC that badly...

As a whole STNH uses far more system resources than vanilla Stellaris as it's simply a much bigger "game", that does significantly more in the background... By comparison vanilla Stellaris is incredibly basic...

I'll look into releasing memory/shutting down services. Can anyone say what the bare minimum for STNH is? Stellaris itself runs smoothly on both my macbook and my win 10 machine.

I have a similar issue. After a long time I reinstalled Stellaris and this mod and even though I have a much better PC now it took more than 10 minutes to load a new game. Had the same issues selecting a race too!

My specs: RTX2070S, 32GB memory, Ryzen 7 3700x, 1TB NVME M2 SSD
reinstalled the game, also onto a different SSD, only this mod is activated.

Just got it running now. If I have ingame performace problems I will write again.

[EDIT]
Ingame seems just fine. No mayor performance issues. I don't have the main screen and loading issues when deactivating this mod. I started another campaign as Romulanians (standard galaxy) and have the same issues again (slow race selection & veeery long loading screen. Expecting it to be around 15 Minutes again..).

What are the min specs I would need to run stnh smoothly?