Linux, Firefox
Ryzen 9 7900x 12 core
RTX 4070 Ti
From my informal measurements (Firefox task list, Gnome process viewer, etc), the game is taking about 90% of one multi-threaded core (probably actually 100%, the difference being due to how it's measured).
Not seeing any GPU impact.
Game responsiveness is instant. Not seeing any slow-down at all.
I just noticed this thread is 4 months old, so maybe I'm playing a newer version of the game that has addressed any performance issues. Might want to include a version number in the UI somewhere.