Yes you should plus in the molex connectors. I would’t push it to 999 watts, you should be at around 88% on that bad boy with full load… Meaning, I wouldnt go past 850 watts ( give or take ) on that with it constantly running like that
Mixmaster is correct and follow his advice, use both molex connections on board and also powered USB risers, these boards can manage 6 cards so leave yourself some upgrade path and buy a 1250w supply for each setup,the more you push these supplies to there max the less efficient they are and that’s important when running 24/7 for years
To be honest, I would do x6 rx470, the hashrate between the two is not far off, you’ll spend about the same BUT get more H/S and less power. IMO tthe 470 is best GPU for power/efficiency/ROI card on market
If you undervolt, should be, I know guys that mine ether with them and draw about 100-110 per card from wall then board and etc… Should be around 750 too 800 should be fine
You seem to have your mind set on a 1000 W power supply but I would suggest again to move up to a 1250 like I first suggested,mining software is improving every week at moment and with faster speeds comes more power used by cards,you will be at limits now, power supply is most important part of your build and better to have extra power in reserve plus they run more efficiently when not running max,you don’t want to base your calculations around having to under volt each card to stay within limits,
Like many have said, I would go with a larger power supply. There is no need for the molex to mobile if you have power risers. However, I would be sure to have an separate molecular connector for each riser (located at the end on SAT 3x connector power cable).