May be worth disabling G-Sync and seeing if it makes a significant difference.
This could potentially be causing conflicts. RAM is only guaranteed compatibility and no conlficts in the form sold (from the same packs) See point 4 here:
https://forums.tomshardware.com/thr...when-selecting-parts-for-a-custom-pc.3510178/
You'll find them all here:
https://www.asus.com/Motherboards/PRIME-X470-PRO/HelpDesk_Download/
What exactly is good?
And do you ever hit 100% at any point on any CPU core or GPU?
Are you streaming too?
Your rig should be able to play most things on highest settings. The CPU may just be a little limiting at times, but not often.
Do you have latest BIOS installed?