As long as the cats are not more than 2-3lbs overweight I wouldn't limit what they are eating unless they start gaining excessive weight. Maintaining a good healthy weight is important as not to strain joints, heart, lung function etc.
The weight issue will come into play more at the later stages of the disease or if Rainbow starts refusing to eat certain flavours/brands. It is important to try to rotate as many different flavours/brands as possible so he'll accept different foods & hopefully won't refuse to eat all but one kind of food.
My experience with raw food is also in the later pages of the sticky thread, my girl passed away a couple of years ago so about the last 4 pages are more about other peoples experiences/questions. I started feeding a ground bone-in prepared raw by a local company, until my girl started having non-CRF related issues with bone. At that point I moved to buying human grade ground chicken, meat only no bone, from a local butcher & adding a powdered premix called TC Feline Plus
(a company highly recommended by her homeopath) to the meat to ensure all essential nutrients were being met, the bone content was so finely ground that it didn't cause her any issues. She was also on a couple of supplements recommended by her homeopath vet as well as a vitamin formulated for senior cats. My girl loved raw & it was never a challenge to get her to eat until the very end