Hi Daza - thanks for posting the GIF of the issue. Are you referring to these lines that appears when moving around? If so, those are seams between tiles that unfortunately show sometimes, more so under certain lighting conditions. I would like to fix these, but I am waiting for the new Godot 3.0 renderer to be released before spending time on the issue. I agree that they are distracting and I am determined that I will do what I can to get rid of them once the new renderer is available. :)
In regards to the other topic, I do have some functionality planned similar to what you described and shown in the video. In the UI Editor, I will have a special editor for creating custom screens with images and text that you can show in your game for cutscenes, etc., so I think that should allow you to do what you are interested in.