I finally got my M5Stack-Pico-D4 flashed with WLED and the interface works great! Now I need to find a GPIO port to use. GPIO 0 is used for flashing and I do not see any other GPIO ports that match the recommended list. I am hesitant to use the I2C or SPI ports because I might want to connect something else, if possible with WLED (I’m still a bit new with the firmware). I suppose I could use the ADCx ports but might want to do reactive sound with it. Unless the device supports I2S (haven’t checked yet). I was hoping someone can share what their favorite GPIO pin they use that doesn’t conflict.
I guess I will be using the OTA feature to update it so probably will not need to use the GPIO 0 again. But I thought I would ask first.
Thanks everyone for your valuable time and help! I appreciate it!!
I’m sorry to reply to my own thread but I did some research I should have done prior to my post. For that, I apologize! I get an idea and act on it, and often enough, figure out how to research it after I click POST.
I might want to connect a SPI or I2C or I2S device to the MCU board, so I figured my WS2812 data line could be G25, G32, or G33. I got my level shifter circuit ready and have it all bread-boarded up. So I will test each GPIO and see if I have any issues. The same level shifter circuit I already used with a ESP32-DevkitC-VIE (external strip power) and it worked GREAT with a 16.4’ string.
BACKGROUND: I have 20 of these M5Stack-Pico-D4’s in hopes to animate various little fixtures around my house. The LED count will be small, per each, so I added either a USB-Micro or USB-C connector board along with 2a usb power modules and appropriate cables to power the little mods. For a run of fixtures, like for on top of our kitchen cabinets, I will run a 12vdc higher current line to tap into with each fixture via step down buck converters to get 5vdc. My house LAN is a bit busy with a lot of home automation devices so at some point I will have to explore using a separate subnet for all these things. But that is for another thread. 
Thanks for listening!
ESP32 can remap any GPIO for any function. The feature is called “muxer”.
I realize that, at least with other ESP32-x varieties I have used. But say with the -S3… some pins are hardware dedicated and are faster. At least for SPI (IE: FSPI), which is why I asked. I decided on using GPIO 33 since it was allowed, not any of the I2C or SPI pins, and I can use I2S for the audio. So I do not need the ADC’s at all. All my sensors I want to use with this device are either SPI or I2C also, no analog.
Thanks for the reply! I always though “muxer” referred to the GPIO matrix and not the IOMUX.