Performance problems On a good Machine..why?

Hello there…

I am sure there might already one or two threads about this and i checked some of them but none really helped me.

My problem is…when i wanna play the game and stream it on twitch at the same time i got massive FPS drops, which make the game stutter alot.
I red many had those problems and they solved it somehow but propably i am too dumb for it… So i hope i can find one or another tip here that could help me.

So when i want to stream it via Streamlabs OBS it wont let me do it with game capture on fullscreen. It freezes just the screen but i can see my mouse moving.

So i have to use Window capture and use Window borderless. And this seem to suck hard on my CPU.

Or maybe its the fact the game is 32Bit and i am using 64.

I really dont know. Tried already stuff like setting affinity of the game to core 0.
Set the game priority to higher than normal.
Changing the maxResourceThreads in the options.txt to 8
Started OBS as administrator.

If someone of you got something else i could try…i am open for suggestions.

My system:
Windows 10 64bit
32GB DDR4 RAM
ASUS Strix GTX 1080ti OC
Intel I7 6700 4x4.0GHZ

Maybe its just my opinion but i think a machine like this should easily run a game like Grim Dawn even though its some years old. But Max setting should be possible even on 4K Res.
Thanks so far