Your CPU usage is at 95% which means that no matter how far you turn down graphical settings, it will not increase your fps. This is because your i5-9400f is responsible for pre-rendering the frames that go to the GPU and once it is running flat out, your fps cannot increase. Turning down graphical settings does not usually decrease the load on the CPU, it decreases the load on the GPU, which is why your GPU utilization is so low. Since your GPU isn't being utilized very much at low settings, turning up your graphical settings and enabling ray tracing increases the load on your GPU (but not your CPU) which is why your frame rate does not go any lower.
The way I see it you have 2 options:
1. The cheap option:
If you don't want to or can't spend any money to fix this, you will be limited to the frame rate you have right now; your CPU sets your maximum frame rate in a given game and apparently the limit of the i5-9400f is roughly 60 fps is warzone. Since you can't overclock your CPU and no amount of tweaking settings will significantly change anything, you'll have to live with 60 fps. Since at 60 fps your 2060 super has plenty of utilization left over, you're best option is to turn up graphical settings until your 2060 super approaches 100% utilization. This way you get both the maximum frame rate your CPU allows and the maximum visual fidelity that your GPU allows.
2. The $$$ option:
If you can't deal with only getting 60 fps in warzone, you'll need a more powerful CPU, no way around it.
Since you have a z370 motherboard, you can upgrade your CPU to something like an i7-9700k (which I have in my build and have played warzone with). By upgrading to this, you'll go from 6 cores and 6 threads to 8 cores and 8 threads. Additionally, your boost clock will increase from a maximum of 4.1 GHz with your 9400f to 5.0-5.1 GHz with a 9700k (if you overclock it). Upgrading to a 9700k will allow you to play Warzone at high fps.
Keep in mind as well that the RTX 2060 super is recommended to be paired with a 550 watt PSU (more than what you have) and additionally the 9700k has a higher power draw than the CPU you already have (especially when overclocked) so if you upgraded to a 9700k you should probably also upgrade your PSU to something like a Corsair RM650x.