Migrated Office 2011 from MBook Pro running Sierra to MBook Air running Monterey. Any issues with installing Microsoft 365 over migrated Office 2011 on Air?

Sable Basilisk wrote:

Is installing Microsoft 365 over migrated Office 2011 on Air risky?

No. It's perfectly safe. It will technically install them separately and will not affect the 2011 installation at all.

How should I uninstall Office 2011 on the Air; Can Office 2011 on the Air be uninstalled safely?

You will need to manually remove anything related to Office 2011 since even the installer app will not work on Monterey. It should be safe as long as you make sure you only remove items related to Microsoft Office 2011.

See Microsoft's own support document for how to remove it:

https://support.microsoft.com/en-us/office/uninstall-office-for-mac-eefa1199-5b58-43af-8a3d-b73dc1a8cae3#ID0EBBD=Office_for_Mac_2011

FYI, When migrating to a different CPU architecture like from Intel to Apple Silicon, it is best not to migrate any apps, but instead download and install the latest versions so you don't end up in situations like this where it can be difficult to fully remove an older app. Same advice applies when migrating to another Mac running a much newer version of macOS, since many times the older apps will no longer be compatible (or make sure they are already running a compatible version). Starting fresh helps to remove some old clutter as well. It is still fine to migrate the settings (may depend on some of the apps though) and home user folder(s).