How useful is Services Breadth sectioon for certification exam ? Is it worth to invest time on that section ?
Not all of it is important from an exam perspective. For example you dont need to know about Machine Learning or Tensor Flow or APIGEE. But it is extremely important to watch the videos that discuss COMPUTE, STORAGE and DATABase options.
Those are very very important videos because it is being discussed which services are zonal/global/multiregional and also the use cases where they should be selected over others. A Lot of questions in exam will be to select the best products for the scenario. I think it would not hurt to know about Tensorflow either =) Its a nice introduction to services. Best of luck with your certification!