One way I think about this is: You get a certain amount of "credits" to spend to create visual hierarchy. Size, color, space, weight, typeface, etc. The goal is to create a clear design while spending as few credits as possible. Some designs over-spend and things feel messy. Some designs under-spend and there's not enough hierarchy to latch onto. A good practice is to start by spending a single credit, see how it feels, and only spend more if it's not clear yet. For example, if you are trying to create visual hierarchy between two pieces of text, try changing only the weight instead of changing both the weight and size at the same time.