I will add more information about ESP32-PICO-D4 later but now I briefly explain how it is useful and easy to use.
I quickly made a web radio consists of ESP32-PICO-D4 and PCM5102A DAC. (This PCB has some error so you can see thin wire jumpers... New modified PCB will reach me soon.) Simply swapping ESP32 module and ESP32-PICO-D4 is enough to make it! Ultra easy!
But web radio board has very limited number of GPIO pinout so I quickly made full-GPIO pinout version! Again it is ultra easy to handle!!