Always save as a .twbx. The .twbx will include the extract and all of the data in one file that a user needs to access. .twbx files are just .zip files with everything included.
more info here: Packaged workbooks and flows: when, why, how
Do you know what impact hidden fields has here? If it is included in the workbook, will hidden rows affect workbook size? Is it better to just remove them from the backend?