Thank you for your reports. We released client and service updates this week, that address many MacOS-specific performance issues. We are also aware of recent performance issues with Microsoft Teams meetings, especially on laptops and when using external monitors.
The team is working to resolve these issues. In the meantime, please find troubleshooting information here: https://docs.microsoft.com/microsoftteams/troubleshoot/known-issues/teams-slow-video-meetings-laptops-4k.