Expression vs. Restraint in Furniture Design

Hi, I'm a researcher at an office furniture company in the US. I do not have a design background. I am interested in conducting research about the balance of restraint and expression when our designers make furniture. What are the pros and cons of each? What does expression vs. restraint mean (form, colors, materials), and in what situations do you lean one way or the other? Overall, how do you balance these things when making your own designs? Finally, are there good resources for understanding this dichotomy? Thanks!