If you do have problems with getting Preference settings to stick, where do you look for the property list file containing them?

As a general principle:

• Apple and App Store apps should now be accessed via ~/Library/Containers/[app signature]/Data/Library/Preferences, where [app signature] is something like com.corpname.appname
• settings which apply to all users, particularly if they apply before a user logs in, are normally in /Library/Preferences
• settings which apply to an individual user, only after they have logged in, are normally in ~/Library/Preferences (that’s the Library folder in your Home folder)
• settings files should be named something like com.corpname.appname.plist, but many still aren’t.

If you’re in doubt, open the Preferences (or other) folder in which you suspect the file is stored, and order the files by time and date last changed, the newest at the top. Open the app/pane, make a change in the Preferences or other settings, and the property list should shoot to the top of the Finder window.

Here is a list of well-known preferences files, for OS X El Capitan 10.11.6. Yosemite was slightly different, and earlier versions even more different. No doubt macOS Sierra will be different again.

Activity Monitor preferences ~/Library/Preferences/com.apple.ActivityMonitor.plist
Airport preferences /Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist
Ambient light sensor /Library/Preferences/com.apple.iokit.AmbientLightSensor.plist
App preference settings ~/Library/Preferences/[app signature].plist
App Store account settings ~/Library/Preferences/com.apple.commerce.plist
App Store autoupdate settings /Library/Preferences/com.apple.commerce.plist
App Store settings ~/Library/Preferences/com.apple.appstore.plist
Apple accounts enabled /Library/Preferences/SystemConfiguration/com.apple.accounts.exists.plist and ~/Library/Preferences/com.apple.accountsd.plist
Apple Magic Mouse gestures ~/Library/Preferences/com.apple.driver.AppleBluetoothMultitouch.mouse.plist
Apple Magic Trackpad ~/Library/Preferences/com.apple.driver.AppleBluetoothMultitouch.trackpad.plist
Apple Remote Desktop /Library/Preferences/com.apple.ARDAgent.plist
Archive Utility ~/Library/Preferences/com.apple.archiveutility.plist
Audio MIDI Setup ~/Library/Preferences/com.apple.audio.AudioMIDISetup.plist
Audio settings /Library/Preferences/Audio/com.apple.audio.DeviceSettings.plist and /Library/Preferences/Audio/com.apple.audio.SystemSettings.plist
Automator ~/Library/Preferences/com.apple.Automator.plist
Bluetooth configuration /Library/Preferences/com.apple.Bluetooth.plist
Calculator exchange rates, etc. ~/Library/Preferences/com.apple.calculateframework.plist
Calendar ~/Library/Preferences/com.apple.iCal.plist
ColorSync calibrations ~/Library/Preferences/com.apple.ColorSyncCalibrator.plist
Contacts ~/Library/Preferences/com.apple.AddressBook.plist
Crash Reporter ~/Library/Preferences/com.apple.CrashReporter.plist
Date & Time menubar clock ~/Library/Preferences/com.apple.menuextra.clock.plist
Date & Time timezone auto setting /Library/Preferences/com.apple.timezone.auto.plist
Desktop ~/Library/Preferences/com.apple.desktop.plist
Dock ~/Library/Preferences/com.apple.dock.plist
Emoji & Symbols palettes ~/Library/Preferences/com.apple.CharacterPaletteIM.plist and ~/Library/Preferences/com.apple.CharacterPicker.plist
Energy Saver settings /Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist
Find My Mac /Library/Preferences/com.apple.FindMyMac.plist
Finder ~/Library/Preferences/com.apple.finder.plist
Help ~/Library/Preferences/com.apple.help.plist
iBooks ~/Library/Preferences/com.apple.bookstoreagent.plist and ~/Library/Preferences/com.apple.ibooks.plist
iMessage ~/Library/Preferences/com.apple.imessage.bag.plist
Infra-red controller /Library/Preferences/com.apple.driver.AppleIRController.plist
iTunes ~/Library/Preferences/com.apple.iTunes.plist
iTunes, Aperture, iPhoto paths ~/Library/Preferences/com.apple.iApps.plist
Keyboard settings before login /Library/Preferences/com.apple.HIToolbox.plist
Keyboard settings after login ~/Library/Preferences/com.apple.HIToolbox.plist
Login window /Library/Preferences/com.apple.loginwindow.plist
Miscellaneous preferences ~/Library/Preferences/com.apple.systempreferences.plist
Network extensions /Library/Preferences/com.apple.networkextension.plist
Network interfaces /Library/Preferences/SystemConfiguration/NetworkInterfaces.plist
Network settings /Library/Preferences/SystemConfiguration/preferences.plist
Network Utility ~/Library/Preferences/com.apple.NetworkUtility.plist
Photos ~/Library/Containers/co.apple.Photos/Data/Library/Preferences/com.apple.Photos.plist
Power Management /Library/Preferences/SystemConfiguration/com.apple.PowerManagement.plist
Printers /Library/Preferences/org.cups.printers.plist
Remote Access servers /Library/Preferences/SystemConfiguration/com.apple.RemoteAccessServers.plist
Safari ~/Library/Preferences/com.apple.Safari.plist
SMB servers /Library/Preferences/SystemConfiguration/com.apple.smb.server.plist
Software updates /Library/Preferences/com.apple.SoftwareUpdate.plist and ~/Library/Preferences/com.apple.commerce.plist
Spaces ~/Library/Preferences/com.apple.spaces.plist
Spotlight ~/Library/Preferences/com.apple.spotlight.plist
Text substitutions (Keyboard pane, Text tab) in an SQLite database in ~/Library/Dictionaries/CoreDataUbiquitySupport/ under your UUID; not readily editable or removable
Time Machine backups /Library/Preferences/com.apple.TimeMachine.plist
Universal Access ~/Library/Preferences/com.apple.universalaccess.plist
User dictionary in an SQLite database in ~/Library/Dictionaries/CoreDataUbiquitySupport/ under your UUID; not readily editable or removable
WiFi settings /Library/Preferences/SystemConfiguration/com.apple.wifi.message-tracer.plist