Hi! Honestly, I think it's a little different for everyone. I'm fluid between xenos but I've identified as pupgender for a while before, which is obviously not the same but maybe similar to catgender (which I briefly identified as). I would also like to point out that I am autistic so this is coming from a neurodivergent perspective! /lh/info
Xenogenders in general in my experience: I don't feel xenic at the moment so it may be a little off, but with any xenogender for me it's just,,, intrinsically connected to my gender. It's kind of like how people assign colors to school subjects, saying math is red or science is green. It's just like an association in that sense. People often say that their gender "feels" nonbinary or "feels" demigender (for example) but for me gender "feels" just,,, differently. It "feels" like the feeling of sitting outside at night with no lights but the moon and listening to ethereal music and feeling the cold air on your face and a sense of peace, with a small part inside you being a little bit scared of both life in general and the present moment. It "feels" intrinsically connected to puppies, especially golden retriever pups, in the way that they are cute, caring, and blissfully ignorant. Also, to be frank, one of my comfort characters I kinned really liked golden retrievers and had a pretty similar personality to a typical golden retriever. I liked him a lot and he was such a a part of me that him and his interests felt woven into my own identity. It's really hard to explain how these can feel connected to gender, but again it's similar to the color-to-school-subject-assigning maybe for me.
As for catgender specifically: I have identified as catgender before, albeit briefly. As you said, it is not inherently identifying as a cat. For me personally, it felt closely related to black cats and "silly" cats specifically. Black cats in the way that they are sleek and sinister on the outside, but they're usually just cute fluffballs. They also remind me of nighttime and superstitions, and also, they're cats and everything a cat stands for and looks like. As for silly cats, they're just so,,, silly, lol. They're cute and bumbling and not the most intelligent./lh And I guess my gender just felt like that. Not only feeling like the traits I described, but also just at the end of the day, intrinsically connected to and defined by cats.
These are all just my experiences. Again, every experience is wildly different and I would encourage you to seek other's experiences. Xenogenders are confusing even to a lot of people that identify as them; as for me personally, they're really hard to explain. I hope you find comfort in your gender identity c: