Maybe you can use parts of my project 
https://wled.discourse.group/t/ws2814-based-power-led-pixel/9869
https://wled.discourse.group/t/once-more-esp8266-based-wled-controller/11130
No separate 5V line, only 24V powerline (12 or 19V also possible), every PCB have a 78xx step down switcher for RS485 and the adresseble driver IC WS2814.
For wiring I’d use 2 line 0,75mm² and 2 line shilded cable 0,14 mm²