if the explained variable is measurable by a number, you must apply quantitatives methods, in case you evaluated a quality or a behavior, you apply the qualitative method
if the explained variable is measurable by a number, you must apply quantitatives methods, in case you evaluated a quality or a behavior, you apply the qualitative method
I would recommend you to mention your research questions so that appropriate methods can be suggested. From what you have mentioned, it seems you would be doing qualitative research. However, there are numerous qualitative methods that can be chosen according to what is it that you want to look at.
You should use both quantitative and qualitative methods of analysis. Quantitative: Set up count sheets for items you want to record while you are reading the cases. Qualitative: Keep track of important elements that are not part of your counts.