Restoring Preferences after downgrade from El Capitan to Yosemite
OS X stores application preferences in a few locations

Restore the files and folders from these locations in your backup:
    /Users/username/Library/Preferences
    /Users/username/Library/Application Support
    /Users/username/Library/Containers

To the corresponding locations for your new user account.
No guarantee though that the plist files from the newer OS X system version will work in the older one though. Try it.