Can you change Netrunner from stable to unstable or testing like Manjaro?
For the manjaro repositories we use you could theoretically. Personally I would not recommend it as we don’t test it or officially support it.
So if something breaks you are basically on your own.
I have agree with leszek, since we do not officially support using the testing or unstable branches, and unless you are willing and able to fix things yourself when they break, I would recommend against anything other than using the stable repositories.