When registering Teams Announcement, I want to register the same horizontal size.

When posting a notice post in Teams (image)
I want the same horizontal size
Will there be an official width in the announcement?

Different post size for each post
I want to integrate

In addition to the video
When uploading to Stream or uploading to Teams
Is there a way to preview?

If you connect to Teams after uploading to YouTube as shown below
I confirmed that the preview is available