Hey!
Based on my experience, fish tend to prefer swimming space rather than hiding places. Therefore, I try to keep my aquascape as open as possible. However, that doesn't mean hiding places are not important. I achieve this by carefully selecting the types of fish I keep. I primarily have two species: angelfish and wrasse (I also have a Moorish idol, but it behaves similarly to an angelfish and has similar care requirements). My angelfish tends to sleep in the rock structures, so I've used Tonga rock to create plenty of inner spaces for them. Most of my wrasses, particularly leopard wrasse, prefer to hide or sleep in the sand. I also have a few fairy/flasher wrasses that utilize 1-inch PVC pipes as hidden spots (Pipes are hidden behind the overflow box) and they hide and sleep in those pipes. Please let me know if anyone have any questions. I am happy to share my experience, my setup, and anything about fish!