Nabu -
Is the USB the only connection required to handle both Video and Touchscreen functions?
No
Or do you need to use the 15 pin VGA for video and the USB for Touchscreen?
Yes
Unfortunatley, you need both the USB and VGA connections for the touchscreen. The USB connection controls the touchscreen and the VGA connection carries the video signal. You can use the screen only with the VGA connection but then you loose the touchscreen capability
without the USB cable connected.
I've ran into problems extending the breakout cable they provide. I've extended it to about 20" but any length after that the picture quality degrades.