If I had several applications to convert from QlikView to Qlik Sense, I would start with a small one just to get the hang of the flow. I would use the Dev Hub tool to convert many of the Dimensions and Measures. but I would probably not use the tool to convert the visualizations. My reason for not auto converting the viz is that the viz conversion part of the tool is very limited. I also find that it's best to rethink the viz when converting and not approach it as a one-for-one.