Hey there! Just to reiterate what @Thehack said, yeah the M2426 isn't stand alone. It requires taking 6 pins from the HDplex's 24 pin output (2x ground, 2x 12v, 1x 5svb, 1x PSON signal).
As for the GPU itself, no mods to the 2070 super in my case were required. In order to do this though you...