What exactly is involved with "Setting up macOS" to take you 3 days?
I just pulled out my old 2015 15-inch MacBook Pro, reformatted the machine and installed Big Sur on it and got it in exact condition needed to continue my work that is on my main driver.... Took me 2 hours tops.
I keep all documents in iCloud Documents, so they sync to all my machines, and I install everything through Homebrew, so once I pull that in, I run `brew bundle install` and let it do it's thing...