From Installer packages and metapackages, to the first for Big Sur with its new boot volume group. RSRs and their demise, and when an upgrade is an update.
System install
Installing and maintaining Mac OS 9.1 was a complex process that could easily occupy you for several hours getting all its components right.
Among the new features of 9.1 was support for the burning of CDs in the Finder, and Finder support for switching between open windows.
The Eclectic Light Company 