How does one override the settings of the sub-folders (having been modified in the past). And to override with the base/root folder's options?
First you would need to delete the settings for any sub-folders modified in the past (see below). Then open a folder in Finder (I don't
think it matters which folder), set its sidebar and column widths and Cmd-J options and hit the "Use as Defaults" button. After that, folders you open should have your new default settings, and you can optionally change an individual folder's layout without affecting your default settings.
To delete existing folders' Finder window settings, you have to enter a command in Terminal.app:
The following command will delete
ALL folders' settings on the boot disk (even other user accounts' settings) and restart Finder (you must be an admin user):
sudo find / -name .DS_Store -delete; killall Finder
If you just want to delete existing settings in your
home directory use this command (this is what I recommend):
find ~ -name .DS_Store -delete; killall Finder
The settings are saved in files named '.DS_Store'. The 'find' commands start at the specified directory (either the root of the boot drive '/' or your home directory '~'), finds all the .DS_Store files, and deletes them (permanently -- they do not go into your Trash).