Better quality is per-person basis.
Some people prefer 60fps, some people prefer a clearer image(using 30fps).
The unofficial official recommendation is 720p30 @2000kbps until you are partnered/have transcoding.
I stream at 540p60, at 2000Kbps. The low resolution helps with keeping good quality at the low bit rate.
yes, watching fullscreen looks bad, but in all honesty, who watches Twitch fullscreen? On mobile 540p looks crystal clear.