Generally, the JPGs that come from your camera have many modifications baked into them to give them the aesthetic that matches the brand. However, the modifications are very heavy handed. Using JPGs that come from the camera for post-processing severely limit what you can do with the image.
Apps like RT keep that to a minimum, especially when the preset is Neutral, giving the user the power to get the most out of the raw file. It takes some getting used to and some discipline but the results are undeniably better. Read Getting Started. It provides a good overview of you need to do.
That said, the original JPGs and embedded preview images can still be good reference material to your post-processing. Evaluate what you like and don’t like about them, then emulate the aspects that you found compelling and add to that according to your personal tastes.