Yes, in this setup I’m using a very basic off-the-shelf relay module that doesn’t have native support in ESPHome, so I integrated it into Home Assistant via MQTT. You can absolutely replace it with a smart switch that connects directly to Home Assistant, which means you won’t need MQTT or the Arduino IDE at all.
I also have another tutorial specifically on how to connect the C4002 to Home Assistant：Building a Native Home Assistant mmWave Presence Sensor with ESPHome on ESP32-C6 —hope that helps!