It is interesting that your focus is on layout. Sometimes that is a good place to start. Once you have dug deep into the layout of Page B you ask what page comes before and after. Sometimes screen flow is a better place to start. You find that you can go from Page A to Page C without ever needing Page B. Suddenly all those layout options for Page B were too much detail too soon. Some times I use wireframes to clarify information architecture even before the flow. What is the most intuitive way to show that each user will have one or more widgets, and some widgets will share weebles? I might use wireframes to work that out before any flow or layout.