Hi,
regarding the cable management I might have an idea. Make a little box out of wood.
The box is mounted to the shelf.
Hang the monitor below the box.
The powercable comes in my case from the bottom, you can see the cable duct.
In the box there’s the rasberry, power outlet, power supply and all cables.
Left and right I put some speakers.
Below is a microphone for Alexa.
Also below the box is a motion detector to switch on / off the screen. Later I added a power off button, a reset button and a power switch, and some leds to show a status without the need to turn on the monitor.
The picture is from 2017 after I made my first installtion.
Since we have a new kitchen, I don’t have a screen at the moment, so I can’t provide more pictures.