After going through several build iterations in this case, I can finally say:
"I AM FINISHED" ...at least for now ;)

The plate next to the motherboard is a black metal plate with a semi translucient plate behind it to have even lightning on the logos.
While using this PC it is hooked up to an external cooling setup with 2x 420mm & 1x 560mm external radiators to achieve low temps, high overclocking and an inaudible noise level.

Specs:

Intel i7 10700k OC
ROG Strix 3090 OC
32GB 3600 Trident Z RAM
MSI MEG Z490 UNIFY
1TB & 2TB NVME SSD
1x 360 EK Coolstream SE (internal) & 2x 420mm + 1x 560mm radiators external
Vector Strix + active Backplate (EKWB)
Velocity Waterblock (EKWB)
1x EK DDC pump (internal) & dual D5 pump (EKWB) (external)
Aquacomputer High Flow 2, Aquacomputer Octo & Farbwerk 360 for fan/temp control and RGB