The encoder tabs contain settings for each encoded file to be created during recording. Codec, quality, wrapper, number of audio channels, which available timecode source is used, whether the file is segmented, which disc drives are used etc. are set here.
Generally speaking the first column choices filter what will be shown in the second column, and all the available choices in this view have already been filtered by the settings on the Input tab. For instance, if the Color format has been set to YUV10, XDCAM will not appear in the list of available codecs because XDCAM is explicitly a YU8 codec.