dall'hands on di anandtech:
"Depending on configuration specifics, Type-C ports and cables can accommodate upwards of 100W of power (5A @ 20V) along with over 20Gbps of data in various forms
...
Finally, through the use of USB alternate mode functionality, Apple is able to also supply DisplayPort over the Type-C connector. Through the alt mode capability, 1, 2, or 4 lanes of USB 3 data can be replaced with alternate protocols, in this case DisplayPort. The final resolution that can be passed though is implementation specific and isn’t available in Apple’s specifications – but based on Core-M’s capabilities I suspect that Apple has it setup to use 2 lanes, which would allow a maximum of 2560x1440 (WQHD). Meanwhile DisplayPort can also be actively converted to other formats, which is what allows Apple to offer HDMI and VGA through adapters."
