So I’ve set up Google Drive as a destination/location for attachments.
I can send Office docs, PDFs that are stored in the drive as actual attachments on an email but I can’t send any Google docs as attachments - even though the doc is open to all to view.
You cannot normally attach a Google Docs file directly from Google drive. This is nothing to do with eM Client, its just how attaching files to an mail client outside of Google docs works.
eg: If you are trying to attach a Google Spreadsheet as per your example above, you have to first convert the sheet to a .xlsx via "File / Download / Microsoft Excel (.xlsx). Then attach that to eM Client once its downloaded to your computer.