Hello!

it's the first time I write here. But i have a question.
to start an audiostream im playroom, Do i need the client? or can I also do that from the webclient?
Regards Stina!

Hello,
the Windows client offers you the best possible support for audio streams, supporting all the popular formats without any major restrictions.

On the Web client, this is a bit more complex, due to various technical/browser limitations.
You will probably have the best success with Safari, as long as you are trying to play an mp3, mp4, aac or m4a stream, since these formats are supported by the browser.
On Firefox, Chrome and most others, mp3 and ogg should be supported, but there is nowadays a different problem: Most browsers no longer allow an app to stream something from a completely different domain than the one you are currently on, so playing any stream won't work, even if the format is supported. This is done to prevent malicious attacks. For some reason, Safari doesn't impose this restriction (I'm personally not very familiar why that is and it surprises me a little since Apple usually has the most strict policies).

In short, unless you are using Safari, you probably won't have a lot of success with audio streams on the Web client, and the Windows client is recommended. If you are however only trying to propose an audio stream that you want others to hear, you can do that from the Web client using any browser. These issues impact only your ability to hear the stream.

I have a question can you actually use VoiceOver to press the start an audio stream button or do you have to use a keyboard shortcut

You have to use the keyboard shortcut, there is no context menu item.