sorry, i dont know much about streaming games or twitch for that matter. i didnt know that you need third party software to stream to twitch.
Try this bloke's Youtube channel (Eposvox), I've found his video-tutorials helpful for my own utilisation of OBS Studio:
To be a Twitch partner, you have to apply for it, but there's some requirements before they consider accepting.
Must have an average concurrent viewership of at least 500 people (not just a one-time peak)
Regular broadcast schedule of at least 3 times a week
Being a partner grants features such as custom chat badges, custom emoticons, subscriber-only chat, exclusion from slow mode. And lastly, unrestricted access to broadcast archives, and video quality.
As far as i'm aware, non-partnered streamers have a cap of 3500kbps, whilst partners can use up to 5000kbps. Although non-partnered streamers stick between 2000kbps - 2800kbps due to a lot of viewers having shitty internet.
Apparently people had been banned for trying to stream at 6000kbps+ as Twitch consider it to be equivalent to a Denial Of Service attack.