Selecting the TIFF (in any of its variants) or PNG export format enables the drop-down list to select the bit depth at which the image will be exported (16 or 8 bits).
By default, the 16-bit option is always selected, since it is the one that allows the image to be exported with the highest possible quality. In addition, exporting the image to 16-bit also makes it easier to further process the image in other software.
However, if you select the JPEG format, you will only be able to export the image at 8-bit, as this is what this format supports. Therefore, if you are going to continue processing the image in other software, it is recommended that you export the image in 16-bit TIFF format.