Media Encoder barely using my GPU and CPU for rendering an AE comp

This is an often-asked question and the answer is far more complicated that you might expect. In your case, it looks like you might just be compressing a file as opposed to rendering a project from Premiere or After Effects? If that's the case, then there is actually an option you can change. First, video encoding often doesn't use the GPU, but not too long ago AME and Premiere added support for Hardware Accelerated H.264 encoding using Intel Quick Sync. If your hardware is supported (which an 8700K is) then this option will be available to you. Note, this is completely different than the Renderer option at the bottom of the Queue panel or anything related to Mercury GPU acceleration, and this only works on H.264 renders.

In the Export Settings > Video Tab > Encoding Settings, choose "Hardware Encoding." You can see from the Encoding panel in your screenshot that you have "Software Encoding" enabled. Switching this option should make a significant difference in your exports.

Again, there's a lot more to understand about how the GPU is utilized and in what circumstances you'll see performance gains, but this is a pretty straightforward one where you should see benefits.