I'm not a fan of the Royal Canin brand. Their cat foods have a lot of filler in them, at least the ones i have looked at. They also take specialty foods to the extreme. There is no nutritional difference for different breeds of cat. There is no nutritional difference between spayed or unspayed indoor cats. I can understand having specific foods for things like kidney issues, or teeth issues, or a cat being overweight, but they take it too far. I feed my cat wellness, they are grain free, don't have tons of fillers, and my cat will actually eat it. If you are needing a limited diet, I recommend natural instincts, they have very high quality foods in various proteins. My friend feeds her cat instinct limited ingredient rabbit, and it works well for her. Her cat has food allergies, and didn't do well on a fish or chicken based food, so the limited ingredient rabbit is great.
Unsure but Royal Canin is pretty respectable in my opinion.