There are no default settings per se; especially for the preferences you enumerated There are “initial” settings that you can add to, modify, or delete, but no defaults you can revert to. There’s also no versioning of these settings.
For the record, things that I want to know the defaults
includes
- mouse speed, keyboard repeat speed
- shortcuts, especially Accessibility shortcuts
- anything related to muscle memory (don't want to muscle-memorize the wrong shortcut)
There is no “default mouse speed.” Each mouse is different, especially the sensitivity of the mouse hardware and its calibration from the factory. This setting allows you to tweak the speed to accommodate your preference. Change the mouse (especially manufacturer) and that previous setting may no longer apply.
There are system wide shortcuts including Accessibility shortcuts that you could consider “defaults.” You can change them of course and they will be listed in the custom shortcuts list that you create. There’s no need to remember these as anything you modify will revert back once you delete the custom shortcut.