"Beauty is in the eye of the beholder" means "different people have different opinions about what or who is beautiful". Example: It’s true that beauty is in the eye of the beholder. I haven’t found any of Mary’s boyfriends attractive.
"All bark and no bite" means "when someone threatens to do things that they are not really willing or able to do". Example: That new manager threatened to fire me again, but I know he won't do it. He's all bark and no bite.