That's exactly the cable I used when I hooked up one 350w (yes I know) and one 650w PSU to a rig with one 1080 and 1080ti and it killed one of the PSU's (I forgot which), I realize - the draw was too much and that 350w does not mean 350w is maximum draw.
Useful
https://youtu.be/MPjj9EejrYg