I am a bit confused, if ordering boards from the site, which version would I get?

Maybe a good solution to the node/gateway dilemma is adding WiFi transport for nodes to MySensors? Then defining one or more WiFi gateways to connect sensors to. You could then use WiFi enabled devices, such as ESP8266 as sensor nodes. You could use these as radio interfaces to Arduino nodes, with their original serial-to-WiFi firmware and treat it much like the RS485 transport.