Well, I wouldn't stream in 1080p as the bitrate to stream it without it pixelating is quite high.(you can also adjust your x264 encoding profile to use more resources but it will hammer your cpu) Also for bitrate I would not go over 2300kbps as you want to account for the people that are watching at lower download speeds. So unless your a twtich partner, I would limit the stream to 720p@2100-2300kbps. You can also use this to get a rough estimate https://obsproject.com/estimator