If you find that the sound output coming from the DualSense controller to be too loud in Final Fantasy XVI, then you can take a look at this guide from Seeking Tech to see how you can lower its volume.
1. The controller volume option was added to FF 16 through a recent patch update. So, make sure you have the latest version of the game downloaded and installed.
2. With the game updated, open it and then head over to the System menu. This can be done by selecting Config from the title screen or switching over to System from the pause screen.
3. Inside of Settings, use the L1 and R1 buttons to make your way over to Sound Settings.
4. From the Sound Settings tab, move the cursor down to Controller Volume, which has the following description:
Adjust controller sound effect volume.
5. By default, Controller Volume is set to 100. In order to lower it, you need to move the slider to the left.
6. Once you are done, you can exit the System menu and then go back to your game. You should notice that the controller sound output should sound quieter than before.