If you have registered a trade for YT, you can then use the same trade for twitch or you have to register a second trade
When you register, you will choose something that is somehow covered.
This does not have to be extra for every platform. (I hope.)
At least this is the case with other business registrations, so that you take a collective approach and not only deal specifically with one thing.
Ask the IHK. They should be able to tell you exactly what that is called.
No you do not need to.
You register business because you "do" something specific. But not where you do it. So you only need to register once.
If your first trade is registered for retail or a craft, then streaming is not included. Then you would have to make an extension (re-registration). Costs about 20 euro.
But if you have registered "Distribution of Media", then that's enough. You have to see if you can subsume the streaming under the main business.
