I've always found clapping to give me general sense of liveliness/damping of room, I've been on both side of equation. I've accumulated many types of acoustic treatments over the years since changes in system may require change of treatments. I mostly rely on items like carpet and tapestries when I need absorption, acoustic panels like Skylines and Synergistic HFT for diffusion. Just a few strategically may be all one needs, easy to overdo it with treatments.
