Being able to categorize a source helps you understand the kind of information it contains, which is a big clue to (1) whether might meet one or more of your information needs and (2) where to look for it and similar sources.
Categorizing sources before you even have them could also help with deciding where you want to take your research, if you want it to be more fact- or opinion-heavy.
With so many sources available, the question usually is not whether sources exist for your project but which ones will best meet your information needs.
You could find many related sources and narrow it down as you continue to develop your research. Not all the sources need to work out on the first try.
Once you have your research question, you’ll need information sources to answer it and meet the other information needs of your research project.
First, you need to identify your research question to even start looking for sources