Yes, I have used the esp8266 Software Serial library by plerup. GitHub - plerup/espsoftwareserial: Implementation of the Arduino software serial for ESP8266
EM-18 works on a 5v logic, while esp8266 works on 3.3v. The nodemcu accepts inputs of 5v without frying the board. Also Logic Levels - SparkFun Learn states that 3.3v and 5v logic levels are compatible as long as the 5v input doesn't fry the 3.3v board.
Could the voltage level differences still be an issue? Is there any way I can read the input as if it was a 3.3v, with just software changes?