SFTP: not used myself, but the machine supports SFTP. The corresponding page in Web UI is titled: "Scan to FTP/SFTP/Network/SharePoint" and "SFTP" is one of the options. I save to a folder defined via network path (e.g. \\Synology\scans\for OCR) it took me some time to understand the syntax, might be similar with SFTP.

Searchable: I suppose the question is whether the device itself does OCR ("text recognition") before storing a document. As far as I know it can't, in any case there is nothing like that in the scan options in the UI. I have defined a folder action in the folder using Abbyy fine Reader, which automatically makes the scanned documents "searchable" using OCR. However, I needed a licence. Depending on the NAS, there may be another option for this

Hope this helps, otherwise please contact me again

PS I am very happy with the device, the shortcuts make it an autonomous ("without PC") device which several people use, e.g. with predefined email recipients or different folders for the scans. I first had the very popular ScanSnap iX 500 - but sold it on as it didn't meet my requirements for autonomy and ease of use at all.