QUICK ANSWERStart with the tool that matches your immediate input.
Open Text to Speech Audio first when its stated purpose matches the result you need now. Use Add Audio to Video only when it solves a separate next task.
This guide is for podcasters, editors, students, and creators. Start with Text to Speech Audio when your immediate task is to convert your file or data with the Text to Speech Audio directly in your browser. Move to Add Audio to Video only when you also need to convert your file or data with the Add Audio to Video directly in your browser.
The goal is not to run two tools automatically. It is to finish the first narrow task, inspect its result, and then decide whether Add Audio to Video solves a genuinely different next step.
These tools cross two task areas. Use the second only when the first result creates a clear need for the next task.