New to the CKCS

My newly adopted Annie is a mature dog. We have a vets appointment next Monday that will hopefully give me a better idea of her age (and whether or not she still needs to be spayed LOL!).
I can see that she has a lot of tartar build up on her teeth, and from this I'm taking a wild guess that she's four or five years plus. She needs a dental, that's for sure.
My son (a male pom of nine years) eats Eukanuba toy kibble with a tiny amount of Beneful top dressing. And I've been giving Annie the same with just a half teaspoon of the Beneful (cause it's yummy LOL).
Her appetite is great. She was a little on the lean side when she came to me (the result of competeing with ten plus other dogs on a cheaper food).
I feed my guys twice a day (I couldn't imagine myself being restricted to one meal a day and I'm way bigger than they are LOL).
I have always fed Maxwell Eukanuba because I'm a firm believer in smaller quantity of higher quality.
But I also know that there are a number of new companies that are producing very good dog food, and that there might be a better food out there than Eukanuba.
Price is not a big deal. These are my kids. Plus they need very little to stay at a healthy, vibrant weight.
Is there anything that I should know about the specific needs of CKCSs?
I want to give her the very best.
She is such a joy to me and I want to do everything that I can to keep her as happy and healthy as possible.

Boy you could go with all sorts of options! Food is a favourite topic here as you'll see from many previous threads.

The main issue is overfeeding, I think. It's good to start from the point of her being in good shape/on the slim side.

You can see some previous thread debating kibbles and all sorts of other options too from raw diets to homecooked. Lots of choice!

Thank you, Karlin!
I will definitely check out those threads you mentioned.
I'm interested in seeing what folks here think of kibble. I've always fed a kibble because we always used to hear that it was better for maintaining healthy teeth. I'm curious to see if this theory is still thought to be true.
I also give my kids Greenies. They absolutely LOVE them and I had heard that they were supposed to be good for dental health.