Share video and audio during meetings is released on Windows. Mac support is now planned for CY20Q3.
Note: Live events support for video and audio is tracked in this item – https://microsoftteams.uservoice.com/forums/555103-public/suggestions/38470144.
Please refer to this page for more info on this feature: https://support.office.com/article/share-system-audio-in-a-teams-meeting-dddede9f-e3d0-4330-873a-fa061a0d8e3b.
Clicking on the join button in an Outlook reminder takes you to the browser to launch Teams today. The work to bypass the browser and directly launch Teams is being worked on. We’ll update when we have more details.