I can’t see any relevant errors in the logs. Had you got them after trying to change frequency, or not?
Post xrandr output as well.
You might want to try linux-lts kernel, if you have it installed, or install it to see.
sudo pacman -Syu linux-lts linux-lts-headers
Reboot and select linux-lts from the boot menu.
Have you ever used any other Linux distro on this system and had better performance?
If your hardware/PC has an option to use one GPU only, you might want to test if the same happens with only Intel, or only Nvidia.
I have no better ideas. Sorry… 