The XDJ-1000MK2 doesn't need a driver for standard USB connection / HID control. The Link Export driver is to allow you to connect a DJM via USB and CDJs or XDJs to the DJM via ethernet so only one USB cable is connected to the computer... but the DJM-750MK2 isn't one of those supported mixers, so you'll need to run a USB cable for each player and the mixer to the computer.
With that done, check in the CONTROL DEVICES section at the bottom of the AUDIO page in rekordbox preferences to see if they all appear.