The newer displays do not all have the ethernet link. Ethernet started with the HX product.
From GRT's product descriptions on their current website:
Sport 10.1: Six serial ports in and out, and dual USB port,s [sic]
Sport EX & Horizon EX: Three serial ports in and out (optional with six), a USB port, and a dedicated magnetometer port, allow for great flexibility within your panel design. An optional ARINC 429 interface can also be added, while still retaining all serial ports, for connectivity with IFR GPS navigators, such as the G430/650/750.
Horizon 10.1: Horizon 10.1 includes 12 serial ports, in and out, and dual USB ports. Multiple display units are coupled via Ethernet.
So... Any EX EFIS and the Mini in any flavor do NOT have ethernet. Ethernet appears to be available in only the Horizon 10.1. Nothing else connects to the Ethernet port, it's just for linking between Horizon 10.1 units.
The high speed option is one which uses an airspeed sensor capable of and accurate across a higher speed range than standard.