What's the difference between the buttons "Update Layout in Place" and "Change Module and Update Fit" when changing the proposal's module?

Update layout in place

This just means you are changing the size of the panels without changing the center point or layout of the design, so this will create gaps in the design. If the module selected is larger than the previous module, the system will auto-remove any panels that are falling off of the roof or covering obstructions as a result of the updated layout. 

Change Module and Update Fit

This will update the fitment of the layout with the panel change, to make sure that we don't have any problems with the new sizing. The center point and layout will be changed with the sizing so the design does not have gaps.