I have done border drawings for neighborhoods and zones through the Mappress Pro editor/creator and it actually works pretty well. There are some tricks to it like if you are drawing lines you need to click the line icon again to stop. The Mappress settings page also applies to the editor in that you need to set keyboard scrolling so when drawing a pollyline you can move the map around. The map editor is really small but works great. I did wish for that enlargement in the future wish list forum.
You can’t draw kml/kmz files at the Google Maps site but you can draw them in Google Earth. I drew some there but I actually like Mappress better. It is easier, and when using a kml or kmz the content of the info-window is made when creating the original file so the Mappress editor cannot be used for that.