Don't forget that buffering issues could also be what's between the streaming server and your isp. If there's a system having routing problems, network issues, or possible throttling along the way.
My setup is very simple. 50mbps, yes.. only 50mbps with 2 z7+ wired, 2 ipad and 2 iphone. No buffering issues.
I could run 5 streams at the same time with no issues and I'm with Spectrum Cable (Time Warner Cable)