data cable not required - it actually works very well with with microphone to loudspeaker. I actually use my iPhone earbuds, connect them to the radio and hang them on the screen of the laptop (my laptop has the microphone near the middle of the top of the screen). Radio mike I just put on the laptop. Radio in VOX mode. Works like a charm. (Just remember to ...
You're confusing the transceiver implementation with mode as is.
Every single mode, as long as it's not used to transported to transport graphics, can be operated without a GUI.
Whether or not an implementation without a GUI exists is a different question, but honestly, coming from a world that's not Windows, this is basically the standard – be it FreeDV, ...
Here's one example:
NUE-PSK is a standalone, battery-operated digital modem using a
Microchip dsPIC microcontroller. The project includes a character
display for transmit and receive text data, and a graphic display
showing band spectrum and tuning indicator. Using GPL open source
software, the modem can be homebrewed for less than $60 parts cost.