Which cable connection are you referring to?
The whole point of using a Wemos D1 Mini or equivalent is you can position it/them at a remote place.
i.e. They are acting as a remote slave (that communicates to the RPi via MQTT protocol).
You just use your RPi as a server running Node-RED and MQTT.
As @bakman2 said... quite a few people on this forum use Wemos D1 Minis to create "systems".
Take a look at one of my student's current project... (as it might give you some ideas).