For the configuration of key values in GAM, does Yield Hub need normal key values or do they need to be custom dimensions?

Yield Hub requires both normal key values and custom dimensions. All key values are needed to enrich the data for better segmentation, to define the optimized group and control group and to set all floor prices. 

Yield Hub uses only one value per custom dimension. This means that we do not multiply custom dimensions and then consume the budget available for custom dimensions.