SyncWith can report on your store's custom metafields. Only product and order metafields are supported, however we're limited to 25 metafields per object type. SyncWith doesn't currently support reporting on product variant metafields or metafields for any other objects other than products and orders. We hope to add support for more metafields in the future.
Custom fields, which are similar to metafields but less structured, are not supported by SyncWith.