The first thing that you do is get a handle on all of the 32-bit applications that you currently use. Install the free Go64 application to determine that list of applications that will not run on Big Sur which would ship on that new Air. Check with the vendor of each 32-bit application that you encounter to determine if they have an updated 64-bit application for Big Sur. Likewise, confirm if your printer/scanner vendor also has provided driver updates after Nov 2020 for compatibility with Big Sur.
If you are using Office 2011 for Mac, you will need to either select a new Microsoft 365 subscription plan, or the single-purchase of Office 2019 for Mac. Microsoft Office subscription applications are in the Mac App Store. There is also the free LibreOffice Suite that will handle your current Office documents on Big Sur.
Perform a Time Machine backup of High Sierra, so that you have personal data and settings that you can provide to the migration assistant in Big Sur when you first boot the Air. That should provide a smooth transition for email, documents, etc.
If a new M1 Air, then there is no Virtual Machine support for Windows or X86_64 Linux guests, and no Boot Camp support.