Microsoft have ported its Office apps to Apple devices with the new chip, including Outlook, Word, Excel, PowerPoint, and OneNote. The apps are actually Universal Apps which run natively on Apple Silicon. You can already download them if you are a lucky owner of the device.
Being native apps, the Office software runs faster and includes other optimizations. Also, the Office suite which is available on the Mac Store, has received a UI update to match the appearance of macOS Big Sur. Microsoft has also announced that its intelligent search box, Tell Me, is also available across Microsoft's Office apps on Mac.
The devices that use Apple Silicon are MacBook Air (M1, version 2020), MacBook Pro (M1, version 2020, 13"), and Mac mini (version 2020).
Also, it is worth noting that the new Outlook app for Mac now supports iCloud accounts. It will also support shared calendars, first for insiders in the Mac Beta channel.
Interested users can get the Office apps for Mac on the Mac App Store.