I think you're doing fine. If you overthink it, you will end up making the design look less natural.
I also think he's doing fine, but under thinking can lead to under achieving. Or a tank that is half as good as it could be with more thought at this stage of the process.
Depends on the goal of the tank. Natural and pleasant are not always the same thing. There are plenty of natural looking scapes that I would prefer never to have in my home, because they're ugly.
IMO the goal is so it looks like no one has thought about it when in fact they thought of everything and placed it very deliberately.