REMEMBER NOT ALL ESP32 PINS ARE INPUT/OUTPUT – SOME ARE INPUT ONLY!!!!
ESP32 Pin List
All of the pin fucntions, default state, etc:
https://www.espressif.com/sites/default/files/1a-esp32_pin_list_en-v0.1.pdf
Peripheral pins assignment
See here
Pull ups / pull downs
Only pins that support both input & output have integrated pull-up and pull-down resistors. Input-only GPIOs 34-39 do not.