Unfortunately, it all depends on the kitty. Generally I would suggest aginst switching food for variety, if you have a good one. The reason I would say that is cats tend to more sensitive tummy's and switching foods on them can leave them with an upset tummy. However, having said all that if you are going to it sounds like you are doing it in the right way. Start mixing in a little and then gradually increase the amount of the new food.

So if you want to switch for coat health then that is not a bad thing.

In my situation I have too totally different kitties. Bob could eat a different food every day and be fine. He has an iron stomach. While Joey on the other hand will get an upset tummy at the drop of a hat.

As for the feel of the fur, that also depends on the cat. It may be that Sammy's fur is just fuffly and Romeo's is smooth silky hair because that is the way that they are. I could not tell you what is right in this. You may want to just call your vet real quick and ask. They may be able to let you know if the feel of the fur is healthy. That is what is most important no matter what the feel. Just Wanted to add that Sammy's fur sounds great to pet.

I unfortunately have no advice on the flax seed oil. I have never heard of using it for kitties. I do know that it contains omega-3 fatty acids that can be good for human vision among other things. Hopefully someone else will have an this.

I hope I have helped a little.