Let's talk about Collaborations and Co-Streams.
Before you jump into a collab with another streamer, it would be a wise idea to get to know them a little first. More so if it is a 1-on-1 collab, less so if it is a massive collab with multiple other people.
With massive collaborations, involving 4 or more streamers (or in some rare cases 75+ streamers), this point is less of a concern as any way you slice it it'll be chaos. Which is generally the name of the game with collabs that huge.
With 1-on-1 collaborations or even collabs with 2 or 3 people, you will want to take some time and research them. Collab streams of this size are highly dependent on you and the other streamer(s) jiving well with each other. Streams like these can derail quickly if there is a lot of awkwardness between the streamers.
So just how does one research another streamer? The best way to do that is simply to visit their streams! Engage with the streamer and their community. If there is playful banter and chatting between you and the streamer, it is a good sign a collaboration with that streamer will end up being entertaining! As a cherry on top, this usually has wildly positive effects on your growth as people get to know you and your personality!
The last thing you will want to do is try to collaborate with a streamer for the express purpose of exposing yourself to a larger audience to try and capture that streamer's community for yourself. This happens quite a bit and does irreparable damage to your brand and your name. There is no better way for you to destroy any hopes of growing than by turning your collaboration into an advertisement. Do not do this, there are much better ways and avenues for you to directly advertise your content, this is not one of them.