Something should I know about how to load XML on runtime game?

I'm developing a little framework to help me out how to handle some 2D stuffs on the scene, like a tilemap, camera control, some helpers and other stuffs to manipulate 2D games.

To approach that I'm storing some data into XML files, so I can easily do that like it below and works very well on editor script or something like that:

 public static T DeserializeXml<T>(this string xml) where T : class
 {
     if (xml == null) return null;

     var s = new XmlSerializer(typeof(T));
     using (var stream = new MemoryStream(Encoding.UTF8.GetBytes(xml)))
     {
         return (T)s.Deserialize(stream);
     }
 }

 public static void SerializeXml<T>(string path, T instance) where T : class
 {
     if (instance == null) return;

     var s = new XmlSerializer(typeof(T));
     //using (TextWriter stream = new StreamWriter(path, false, Encoding.UTF8))
     using (var stream = new FileStream(path, FileMode.Create))
     {
         s.Serialize(stream, instance);
         stream.Dispose();
         stream.Close();
     }
 }

However I wonder about how to make it possible (save and load) XML files on execution time regardless the platform it is running. Unity documentation is unclear, so there is some approaches that make it possible but other don't.

Questions:

• Have I need to put all XMLs in a "Resources" folder to make it visible regardless the platform?

• Have I need to use Application.streamingAssetsPath and store all XMLs in a "StreamingAssets" folder to make it possibile?

• Or maybe I need to make the both solutions above to turn it possible?

• Something else completely different?

I'm confused what I have to do to make it possible for all situations.

Thanks in advance, guys!