RN4020 BLE module authentication without I/O Capabilities and mysterious datasheet
The I/O capabilities bitmask value is 0x000E0000 and the binary values you list are the 3 MSBs in the "E".

I have used these modes:
Display only - the RN4020 UART outputs a 6-digit passcode which must be entered in the connecting device.
Keyboard only - the connecting device is sent a passcode which must be entered on an input device connected to the RN4020.

I also tried No input, no output and was unsuccessful in connecting.  I haven't figured out how to store a fixed PIN that the connecting device must enter.