All of these subjects kind of tie together and determine the video quality your viewers will experience.
If your video-stream was a canvas, your bitrate would represent the amount of paint you are allowed to use on that canvas. If your canvas is too big, then you can’t make it look good with only a few brushes of paint.
Many streamers make the mistake of thinking they -HAVE- to stream at 1080p60fps and that 720p simply isn’t good enough, when in reality 1080p is very hard to comfortably achieve.
Just think about the difference in numbers.
720×480(Standard DVD) =
Below are Twitch’s recommended video settings, although I would try to push the bitrate a bit further at 1080p. The problem is that might be more than their ingest server can handle, so going beyond 6000 might cause more framedrops, which is why I generally recommend against streaming at 1080p.