You wouldn't use this type of product without first clear coating. Ceramic coatings are really just meant to improve a car's ability to resist water, dirt, bugs, etc. It makes it a lot easier to clean. They are essentially to clear coat what clear coat is to paint. It will only protect against the most minor types of scratches, like maybe using a dirty microfiber cloth. But for any meaningful types of wear, it will do almost nothing -- that's not what it's for.
As for pinball, the only real advantage it may have is keeping the playfield clean and it would likely speed the ball up incredibly, the ball may even start to slide instead of roll. It would be worth trying, but probably not too much value. The ball will beat the hell out of it. And they don't last forever, no matter what the manufacturer says. On a car you will get several years out of it, but on a pinball playfield I imagine it'd wear rather quickly. At least where the ball travels.