As Rahul says, more specific tags are better than fewer generic ones. We just have to ensure that the tagging practice for these questions is done logically.
For prototyping, unless it's a specific Axure (or Balsamiq) question then these questions should just be tagged:
but if it's a specific prototyping question about Axure then it should be tagged:
This is a similar approach to how gaming.stackexchange handle tags:
If you have a question regarding how to solve a puzzle in Skyrim for example then the question is tagged skyrim but if you have a Skyrim question that would only be relevant to PC users (such as how to work with modifications) then they would be tagged skyrim pc