Not sure –what do you mean by "using" notes? Jotting down pointers and observations as you study is very helpful for the learning process. If you don't know the answer to a question without checking your notes, I'd say you should check them. Then, once you've figured out the answer, you can still tap "I don't know" so that your mastery for that term doesn't go up (which would make it appear less often in quizzes and prevent you from practicing it).
Writing notes is not cheating. It's a good memorization exercise. Looking at your notes for the answers during the quizzes absolutely is cheating, though.
SRS only works if you're using your memory. The point isn't to get the right answer, it's to practice the terms you haven't memorized until they are memorized. If you're looking down at your notes to find the "correct answer", you're not engaging your brain and won't memorize anything.
tl;dr: You can write notes if you want, but absolutely do not look at them during renshuu's quizzes.
