Pegasus Flight & Entity Design Coding Help

I want to make a new mob called a Pegasus, a flying steed you can fly against the void with in my new dimension called "Beanstalk Isles" I'm doing it as a datapack because it's what I love to do, but I've never designed a flying mob nor do I know the best way to make it be a custom mob, what entity base should I use for the model to render off of? I usually default to zombies or skeletons. How do I make it fly I was gonna use WASD predicate files along with up.
Along with having someone to help me code would be nice.