Bunch of misinformation in here. The pcie slot is rated for 75w, unless there is something wrong with the voltage balancing on the card it will never go above this. Typically power draw at lower loads, even on a 3090, isn't going to exceed 60w when mining on a properly undervolted card. I've run sata on all kinds of cards over the years with all kinds of algos, including a bunch of 1080tis, 2080tis, 3080s and 3090s with 0 issues. Few simple rules if you do this.

1. Never ever daisy chain. 1 card per cable.
2. High quality PSU with good cables. Cheap PSU with cheap high gauge cables? Don't do it.
3. Never use extensions

That said, you're better off powering them with molex or pcie connectors for added safety as those cables will have higher gauge wire and can handle more power. Often upwards of double the spec if they're quality cables. Don't cheap out on power delivery for mining. DYOR.