That board has a triac in it and you can not use PWM for dimming lights. You need to use phase control. That is to vary the time before triggering the triac, measured from each zero crossing of the AC waveform.
https://electronics.stackexchange.com/q ... ght-dimmerThe ESP8266 is not very for doing phase control because there will be times when the background processes will run and the triggering of the triac will not be consistently timed. This will cause flicker of the light.
Phase control can be effectively done with incandescent lamps. If you want to control LED lamps directly powered from the AC line then you most likely will have other problems to deal with. Weird things can happen when trying to use triacs to dimm some LED lights. Some of the problems can be overcome by having an incandescent lamp in parallel with the LED lamps.