Matters mostly for shirtless photos or maybe if you game beaches and pool parties, because in clothes women only care if you dont have a dad bod.
And yes to get a six pack you gotta diet down to 10-12% body fat, depending on your genetics. If youre chubby id recommend doing it at least one time because you might end up looking great, but if youre of a skinnier build then you might just look scrawny in clothes and most ladies wont be impressed.
You can grow ab muscles as any other muscles by exercising, but it will only make them pop out little more when you're very lean. Example exercises: ab wheel rollout, hanging leg raises, ab machines (but no magic here, you can google some more)