I've never had any luck with anything larger than 4096x2048@60fps on the Go.
3840x1920@60fps h.265 seems to be the sweet spot as far as I can tell.
I'm using Universal Media Server on a Windows system to stream videos to the Go without transcoding over a 5 GHz WiFi link. Works great, no issues with 3840x1920@60fps h.265.