Set up a Now TV Smart stick for my father in law fed via a 4G WiFi router. Smart stick was only device running on the 5GHz WiFi channel and picture quality was appalling. Any scene change/movement caused severe softness and pixelation that slowly cleared just in time for next scene change.
Have read that you need roughly 3.5Mbps for Sky Sports via Now TV. Speed tests on feed showed speed was consistently 8-9Mbps both up and down and a ping time to test server of around 75msecs. So should be well in excess of what is needed.