Review on 🔌 Enhanced Songhe Mega2560 + WiFi R3: Mega NodeMCU with USB-TTL CH340G, ATmega2560, ESP8266 32Mb Memory – Arduino & WeMos ESP8266 Compatible by Greg Mcnealey

Works as advertised. I had no problem uploading to esp8266 or Arduino Mega. I also had no problem passing serial number from esp6266 to Arduino. When sending a serial number from the esp8266 to the Arduino, switches 1 and 2 must be on. The sw switch also selects where you send the serial number from the esp8266 to either serial number 0 or serial number 3 on the Arduino. If you choose serial number 0, make sure dip switches 3 and 4 are off as this will conflict with the onboard UART. Not sure yet what the mode switch next to the ESP chip does. But I've successfully connected to wifi to get the time from ntp and passed that to Arduino as a serial string to display on an array of LEDs with a common anode to show the time.