Don's Home Technology Macintosh How to transfer Apps to a new Mac
Notes from macnexus | Sacramento User Group
Cleanup apps don't do a very good job
Apple's Migration Assistant is selective and very good now
Best to only copy documents
Reload apps from the web
Don't move apps so you clean up 32-bit apps and other old apps
Do a time machine backup first so you can get apps you might need
Don't use timemachine

May need to check icloud settings
Don't copy library

32-bit check
32-bitCheck & ArchiChect – The Eclectic Light Company
How to check if your Mac’s software is 32- or 64-bit Macworld

macOS - How to Upgrade to Big Sur - Apple
Upgrading to the Very Latest Macintosh OS | Randy Singer 2020
Restore your Mac from a backup - Apple Support
Move your content to a new Mac - Apple Support 2021
[Update: Mar. 16] macOS Big Sur update bugs & issues tracker - PiunikaWeb

Mac OS Issues:
macOS Big Sur update bugs & issues tracker Nov 28, 2020
Go64 St. Clair Software
How to get old versions of macOS - Apple Support

2008 links:
Mac OS X 10.5: Using Migration Assistant to transfer files from another Mac at
Move All Your Stuff to a New Mac -- Quick with Migration Assistant
MacBook Air: How to use Migration Assistant
Tiger's Powerful Migration Assistant | O'Reilly Media
How to Transfer Mac OS X Application Data between Computers at Professional PHP