Yes, a compatible coating increases water repellency and makes washing easier. Before applying film, however, any existing ceramic is usually removed, otherwise the film adheres less well.
Yes, if the formula is intended for that material and does not change the appearance. Matte finishes need dedicated products: standard ones add gloss, which a matte surface does not want.
Wax gives gloss and protection for a few weeks. A ceramic coating lasts incomparably longer and makes washing easier. Film is the only one that physically protects the body from stones — ceramic does not.