Question is above
CPU and GPU utilization constantly between 30-45%.
Did some research on the internet and found nothing really useful: /
This is probably due to the fact that your computer has more than enough resources / performance and only needs some of them.
Isn't there a way that you can do something so that you can achieve more FPS in games?
When it comes to Fortnite, check the options to see if the fps are limited there. If so, raise them to the desired number. This also works with many other games.
You have to see if something unnecessary is running in the background, and then reduce the quality.