Device Boot Overlays

I have managed to successfully connect my wifi featherwing to the Giant Board and to my local network by following the guide in your documentation and editing UEnv.txt. I also see your example for enabling the PWM, which also involves adding and uncommenting .dtbo files. Now I want to enable other peripherals, like the ADC.

Are all .dtbo files for all pins and their functions already included in the image you distributed?
Where can I look up these .dtbo files to see which ones to use?
If the .dtbo file isn’t included with the image you distributed, how do I add it?
If the .dtbo file is somewhere in the file directory on my giant board’s SD card, where is it?

Edit: One more question.
Enable_uboot_overlays = 1

is that 1, as in the flag is true? Like I’m not changing it to 2 if I’m adding another overlay like PWM, right?

I found the overlays folder and it has pwm, i2c, i2s, Ethernet, LCD and UART. I suppose I have to write my own for the ADC pins, or is that somewhere in the Adafruit documentation? I assume they will have to be renamed with GB in front. What IDE editor can I use? They don’t open properly in notepad or notepad++.

I would have a look at this. The ADC setup is a bit different from other peripherals. Giant Board SBC contest