After researching the topic I got an impression that featuring a product on a stream or instagram is more powerful than ads on youttube and instagram. Is it true? In tha case it looks like that more and more companies should start allocation most of the marketing money towards accessing the customers via the social media channel and the influencers. Would be happy to read some good article and analytics on this topic.
You are asking a very broad question. It is going to be very different for every brand. It really depends on each brands goals. A company might find that they get a better return on advertising spend when partnering with a Twitch streamer than running a YouTube ad, but for a different brand it could be the complete opposite. Each brand will have to test their own strategies to discover what works best for their company.