The Setup->File Associations->Use Both FS+WPS Associations menu item is used to toggle the priority of FS/2 associations over any conflicting defined WPS associations. When checked on, FS/2 associations have priority over WPS associations.
It is recommended that this option be enabled (default setup) and that the Setup->File Associations->Default to WPS Associations menu item be disabled (checked off). This setup will always use the FS/2 associations in priority over WPS associations but if there is no defined FS/2 association for a file, then the WPS associations will be used.