I am not exactly sure how to transfer files by Bluetooth, if you need an app for that. As a test I did associate my old Samsung S3 with my J7 using Bluetooth, and there is a Sync button that appears to be active, but I do not know exactly what that does if it syncs all files or specific ones.
Another alternative might be if WiFi hotspot was enabled on one of the devices, to transfer files using sftp. It helps to be somewhat familiar with Linux or other *nix like OS for generating ssh keys and how to use them. AndFTP is a good sftp client. Not sure of a good sshd (server) app. The SSHServer app that I used on my old phone I could not seem to configure on my new phone. SimpleSSHD works, but works best with keys, because password connection is just temporary and you have to look on the other device for the password. But that is not necessary once you have a public key put into "ssh/authorized_keys" on the server end (in internal storage even though SimpleSSHD shows it in /sdcard/ssh). In this case your phone would likely be the WiFi hotspot and use AndFTP (with private ssh key) as client to connect to an ssh server on the tablet.
One issue I ran into is that I have not found an ssh server app that has write permission for SD or microSD card on newer Android versions, but they have permission to write to internal storage. Note that /sdcard is not really the SD card, that loops back to internal storage (same as /storage/emulated/0). The SD or microSD is actually under /storage/UUID which for default formatted SD may be /storage/0000-0000, but if reformatted may be some other 4 hex digits, dash, 4 hex digits. AndFTP can get into either internal storage or card storage, but not at the same time. So I set up one connection for internal storage as home and another connection with SD or microSD as home.
