This migration is usually quite transparent, but there are some very old MacBook Air models, and some very old apps…
The stuff that won’t work well on newer macOS includes 32-bit apps, such as when moving from macOS 10.14 and earlier, and those apps that need now-deprecated kext support, and such.
Very old Microsoft Office (versions prior to 2016) won’t come across either, but the old Office files and documents will. The Office apps prior to 2016 are 32-bit apps.
The existing MacBoor Air and its contents are not modified, so you’ll still have recourse; all of that is still available, should you need to resolve something (not) on the new Mac. That can include a second migration, if you want.