Can I connect a tablet device to XDJ-RX and use it?

You can play the tracks on a tablet device by connecting the tablet device to the USB-A terminal of the XDJ-RX by using a USB cable, or by connecting the tablet device to the wireless router wired to the LAN terminal of the XDJ-RX.
rekordbox (iOS/Android) must be installed on the tablet device.

It is, however, necessary to update the firmware of the XDJ-RX when using rekordbox (Android).
For details, see the link.