Both mean approximately the same thing, yes. #1 is better, in my opinion, because it doesn't have the extra words in it!
Yes, "someone who works in a garden, growing plants and making it look attractive" and "someone who works in a garden, while he grows plants and makes it look attractive" both describe the same meaning, which is a gardener. The two statements are slightly different in their word choice and syntax, but the essence of the meaning is the same. In both cases, a gardener is someone who cultivates and cares for plants in a garden with the intention of making it visually appealing.