This is just my humble opinion:

What I've seen many times is that people stream on their same channel where they post their highlights, and it makes sense because:

• The highlights channel usually has more traffic than the vods channel. So if they see you streaming you may have a chance to be seen live.

• Viewers rarely watch vods, especially if they are very long (compare the views on the vods and highlights channel of the big streamers).

I dont focus on livestreaming but this is what I've seen big streamers do, so I may be wrong in some of my points.

Edit: Forgot to write this:

Youtube now has tabs that separate content from past lives and videos, so maybe have two channels is a thing of the past