First, very nice! Lots of goodies!
Second: re: rocks. There is no ideal size. All depends on what you want and what will fit and how. Bigger/heavier rocks help hold the scape in place. I only have a few key pieces glued. Rest are stacked like a jigsaw puzzle. I place them and turn them until they fit as close as possible without rocking and feel stable with my testing. Another rock added on top usually makes it even more stable. Having had to tear down my rocks to catch and remove fish, I learned rocks sometimes have to come back out and of course, they won't go back in the same way...
Aim for terraces/stepping up. Harder with a 3 ft long (like mine) I ended up going a wall but not enough good terraces for corals. Excited to see what you come up with. Take your time and enjoy the journey