<ComboBox ItemsSource="{Binding Settings}" DisplayMemberPath="Name"
          SelectedItem="{Binding SelectedSetting}" />

public ObservableCollection<UserSettings> Settings { get; set; }

private UserSettings _selectedSetting;
public UserSettings SelectedSetting
{
    get => _selectedSetting;
    set
    {
        _selectedSetting = value;
        OnPropertyChanged("SelectedSetting");
        OnPropertyChanged("UserStringSettingsHandler");
        OnPropertyChanged("UserSlideSettingsHandler");
    }
}

public UserSettingsViewModelHandler<string> UserStringSettingsHandler { get; set; }
public UserSettingsViewModelHandler<SlideSettings> UserSlideSettingsHandler { get; set; }

public class ApplicationSettingsViewModelHandler<TReturnType> : AbstractApplicationSettingsViewModelHandler<AppSettings, TReturnType>, INotifyPropertyChanged
{
    public ApplicationSettingsViewModelHandler(AppSettings settings) : base(settings)
    {
    }
}

public class UserSettingsViewModelHandler<TReturnType> : AbstractApplicationSettingsViewModelHandler<UserSettings, TReturnType>, INotifyPropertyChanged
{
    public UserSettingsViewModelHandler(UserSettings settings) : base(settings)
    {
    }
}

public abstract class AbstractApplicationSettingsViewModelHandler<TSettingsType, TReturnType> : INotifyPropertyChanged
{
    private TSettingsType _settings;

    public event PropertyChangedEventHandler PropertyChanged;

    public AbstractApplicationSettingsViewModelHandler(TSettingsType settings)
    {
        _settings = settings;
        _values = new Dictionary<string, TReturnType>();

        MapSettings();

        PropertyChanged += OnApplicationSettingsChanged;
    }

    private void MapSettings()
    {
        var settingsType = typeof(TSettingsType);

        var properties = settingsType.GetProperties().Where(prop => prop.CanRead && prop.CanWrite);
        foreach(var prop in properties)
        {
            try
            {
                if (prop.GetValue(_settings) is TReturnType val)
                {
                    this[prop.Name] = val;
                }
            } catch(TargetParameterCountException) { }
        }
    }

    private Dictionary<string, TReturnType> _values;
    public TReturnType this[string key]
    {
        get => _values[key];
        set
        {
            _values[key] = value;
            OnPropertyChanged(key);
        }
    }

    private void OnApplicationSettingsChanged(object sender, PropertyChangedEventArgs args)
    {
        if (!_values.ContainsKey(args.PropertyName))
            return;

        var settingsType = typeof(TSettingsType);

        var property = settingsType
            .GetProperties()
            .Where(prop => prop.CanRead && prop.CanWrite)
            .FirstOrDefault(prop => prop.Name == args.PropertyName);

        if(property != null)
        {
            property.SetValue(_settings, this[args.PropertyName], null);
            AppSettings.Default.Save();
        }
    }

    public void OnPropertyChanged(string propertyName)
    {
        PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
}

public ReportingWindowViewModel()
{
    Settings = new ObservableCollection<UserSettings>(AppSettings.Default.AllUserSettings);


    AnalyticsHandler = new AnalyticsViewModelHandler<ReportingWindowViewModel>(this);

    PropertyChanged += OnSelectedSetting;

    SelectedSetting = AppSettings.Default.CurrentUserSettings;
}

private void OnSelectedSetting(object sender, PropertyChangedEventArgs args)
{
    if (args.PropertyName != "SelectedSetting")
        return;

    var appSettings = AppSettings.Default;

    var selectedSettingsIndex = Settings.IndexOf(SelectedSetting);
    appSettings.SetCurrentUserSettings(selectedSettingsIndex);

    UserStringSettingsHandler = new UserSettingsViewModelHandler<string>(appSettings.CurrentUserSettings);
    UserSlideSettingsHandler = new UserSettingsViewModelHandler<SlideSettings>(appSettings.CurrentUserSettings);
}

<TextBox Text="{Binding UserStringSettingsHandler[Name]}" />