Screwed up my PSU for RX 9070 XT

The RX 9070 XT has 3x 8 PIN PCIe connectors, while the PSU I got has only 1x12 pin 600 Watt rated daisy chained into 2x 8 PIN PCIe.

If I use only the 2x 8 PINs, would that damage the card or only lower my performance?

I found an extra PCIe cable from another PSU, but it doesn't fit into the new PSU, making me think that every PSU has different input ports and that I won't be able to find a cable separately.