These mean the same thing. Elihu is emphasizing that he is now ready to speak. His "tongue" speaking represents himself speaking. AT: "I have opened my mouth and I have begun to speak" (See: [[rc://en/ta/man/translate/figs-parallelism]] and [[rc://en/ta/man/translate/figs-metonymy]])
Here Elihu refers to himself by his "heart" as he speaks of being upright. AT: "I will speak with uprightness" or "I will speak with complete honesty" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
Here Elihu refers to himself by his "lips" to emphasize his speech. AT: "I will speak sincerely to you the things I know" (See: [[rc://en/ta/man/translate/figs-synecdoche]])