Your going to want to know the KH, or at least the people that your asking for help from, should a problem arise.
And IDK doesn't get it.
I just think its good to know what both are when I start out.
You probably won't find the need to replace them later on. But its good to at least know what your starting with, instead of guessing.
the ammonia thing was just soemthing t make life easier while doing the cycle for the first time ever. And for $4 thats alot of testing. And being new to this your liable to find yourself about out of drops by the end of the first week.
You can test the stick in thing with the ammonia test in your kit.
But yea, its just an option thrown out their. You might find it isn't accurate or something?
Like I said somewhere, I could be testing mine against drops tomarrow, if I cause an ammonia spike with some change overs I have plannned.