Vector2 Editor Visualization

Another option could be to use the previewGUI for this. Idea is similar to the other answer you posted, but added some logic to convert units to pixels and center it. You can ofcourse copy/paste the code in DrawPreview to OnInspectorGUI where you can get the original rect using

Rect rect = EditorGUILayout.GetControlRect(false, heightInPixels);

if you prefer to do that instead.

 [CustomEditor(typeof(Example))]
 public class ExampleInspector : Editor
 {
     private SerializedProperty _vectors;
 
     private void OnEnable()
     {
         _vectors = serializedObject.FindProperty("vectors");
     }
 
     // Helper method to get a square rectangle of the correct aspect ratio
     private Rect GetCenteredRect(Rect rect, float aspect = 1f)
     {
         Vector2 size = rect.size;
         size.x = Mathf.Min(size.x, rect.size.y * aspect);
         size.y = Mathf.Min(size.y, rect.size.x / aspect);
 
         Vector2 pos = rect.min + (rect.size - size) * 0.5f;
         return new Rect(pos, size);
     }
 
     public override bool HasPreviewGUI()
     {
         return true;
     }
 
 
     public override GUIContent GetPreviewTitle()
     {
         return new GUIContent("My example");
     }
 
     public override void DrawPreview(Rect rect)
     {
         rect = GetCenteredRect(rect);
 
         // Draw background of the rect we plot points in
         EditorGUI.DrawRect(rect, new Color(0.8f, 0.8f, 0.8f));
 
         float dotSize = 5; // size in pixels of the point we draw
         float halfDotSize = dotSize * 0.5f;
 
         float viewportSize = 10; // size of our viewport in Units
         // a value of 10 means we can display any vector from -5,-5 to 5,5 within our rect.
         // change this value for your needs

 
         for (int i = 0; i < _vectors.arraySize; i++)
         {
             SerializedProperty vectorProperty = _vectors.GetArrayElementAtIndex(i);
 
             Vector2 vector = vectorProperty.vector2Value;
 
             Vector2 normalizedPosition = vector / new Vector2(viewportSize, -viewportSize);
 
             if (Mathf.Abs(normalizedPosition.x) > 0.5f || Mathf.Abs(normalizedPosition.y) > 0.5f)
             {
                 // don't draw points outside our viewport
                 continue;
             }
 
             Vector2 pixelPosition = rect.center + rect.size * normalizedPosition;
 
             EditorGUI.DrawRect(new Rect(pixelPosition.x - halfDotSize, pixelPosition.y - halfDotSize, dotSize, dotSize), Color.blue);
         }
     }
 }