What is the difference between MCU and TTL screens?
The RGB interface means your display will use some of the pins to input 24-bit RGB color data and some control signals. The Adafruit board supports an RGB interface.

Some displays also have a MCU interface option where a parallel or serial bus is used to access frame buffer memory in the display itself, for drawing pixels, lines, etc. under software control. As you are using the RGB interface you don't have to be concerned about this. It just means your display can use either interface depending on the application.

On your display's ribbon cable there will be several pins used to select which interface to use. Pull the pins high or low (as documented in the display datasheet) to select the RGB interface. While you'll need to check the display datasheet and compare it to the Adafruit schematics and TFP401 datasheet, most likely the signals used by the RGB interface will be a 1:1 match between the the display and board.