I think you are on the right track with organization. I don't know what style of aquascaping floats your boat but that will be something to consider as you prepare this tank for the AGA contest. The style will determine the organization of the the layout to a degree. You have healthy, good groupings of plants you just need to figure out how you want to make it cohesive or flow together and go for it. I could drone on for hours because this the theory behind the art. I do know this much from experience is that you want to have a plan, an idea, a picture in your mind's eye of what you want this tank to look like when you snap the photo. Let that be your guide and even if the judges don't like it you will and that's really all that matters.