Hello.
Let's speak about my example:
Gigabyte X570 mainboard + 32GB RAM + 5800x3d+RX7800XT.
I play 90% Throne and Liberty.
This is based on Unreal engine.
In my case i get 120 FPS in static parts and around 80 FPS in crowded area with much action.
On "bosses" or in mass pvp i get around 60 FPS.
All this at 4k with settings on max.
A few details like volumetric fog and like that are lowered to max out the fps.
But you are encountering a strange behavior with you CPU.
In my case , my CPU is relaxed at around 30-50 %
Indeed the GPU is working hard , more then 90% loaded all the time.
What windows do you use and what driver ?
EDITED: I tested with game in a windows. I noticed that the GPU all the time is at peak, at 100%. On the other hand i noticed that the CPU is using usually 50% but in some cases it went up to 97%.
Of course for short period of time.
So i think that this is normal to you either.