@FormElement.UserInitials @* You should see here things like "one", "two", "three" and that is what the combo dropdown should show *@
<br />

<TelerikComboBox Data="@Users"
                 @bind-Value="@FormElement.UserInitials"
                 ValueField="Dto.UserInitials"
                 TextField="Dto.UserInitials">
</TelerikComboBox>

@code{
    public List<User> Users { get; set; } = new List<User>()
    {
        new User{ Dto = new UserSubProperties { UserInitials = "one"   } },
        new User{ Dto = new UserSubProperties { UserInitials = "two"   } },
        new User{ Dto = new UserSubProperties { UserInitials = "three" } }
    };

    public TheFormModel FormElement { get; set; } = new TheFormModel() { UserInitials = "two" };

    public class User
    {
        //bunch of properties
        public UserSubProperties Dto { get; set; }
    }

    public class UserSubProperties
    {
        public string UserInitials { get; set; }
    }

    public class TheFormModel
    {
        public string UserInitials { get; set; }
    }
}

@FormElement.UserInitials
<br/>
<TelerikComboBox Data="@ComboData"
                 @bind-Value="@FormElement.UserInitials"
                 ValueField="UserInitials"
                 TextField="UserInitials">
</TelerikComboBox>

@code{
    List<UserSubProperties> ComboData { get; set; }

    public class Users
    {
        //bunch of properties
        public UserSubProperties Dto { get; set; }
    }

    public class UserSubProperties
    {
        public string UserInitials { get; set; }
    }

    public class TheFormModel
    {
        public int Id { get; set; }
        public string UserInitials { get; set; }
    }

    TheFormModel FormElement { get; set; }

    protected override async Task OnInitializedAsync()
    {
        // use the actual business logic to fetch the data, this is just to get the sample running
        FormElement = new TheFormModel() { Id = 123, UserInitials = "item2" };
        ComboData = Enumerable.Range(1, 7).Select(x => new UserSubProperties { UserInitials = $"item{x}" }).ToList();
    }
}