definitely consider the plants you'll be using as you decide on the hardscape. Too many rocks will limit what you can have, unless you lean heavy on epiphytes. But the look may not matter as much as you think. I spent so much time (and a fair penny!) on figuring out my hardscape, laying it out just like you are doing. Only to find out months later I can hardly see any of them since they're always hidden by the plants. If yours is going to coming out the water that part will probably be fine, but depending on the plants the underwater part might be fairly irrelevant.