If any wired connections to the Duo are required the addition of the connect box (Formation Audio) is required.
This costs an additional £600 and is not included with the speakers.
That will give you 1 digital (toslink) and one set of rca's.
This seems rather expensive.
However, if streaming is all one requires then the above is not necessary and imho makes a more value proposition.
The speaker uses WiFi exclusively. However, it creates its own wireless mesh network to communicate between the speakers and other Formation devices. I am not entirely sure how that works and if there is an impact if you are unfortunate enough and live in flaky reception area. - Although the speakers have an Ethernet port, that can not be used to connect the speakers to each other as far as I can see (unlike Kef's LS50 Wireless Meta's which can also be connected to each other via a Cat5/6/7/8 and can be used even without Wifi ) There is no remote either so your phone/tablet etc is required. Again, the Kef and some others have this as well as more input options out of the box.
Maybe Jaxwire can jime in if I got it wrong.