Difference between SATA-II and SATA-III cables? + What's wrong with PCI-E power supply?

Question

Solid State Drives

Sorry, I climbed the Internet, but I did not understand anything. Does it matter which cable I buy? If I buy a SATA -150, plug it into an SSD on one side and SATA-3 on the other, will I be guaranteed the high speed of SATA3? And more... What is this 8pin cable? Why does it have 7 'pins' on the 8pin side and 2 wires going into one of the 'pins'...

Answer 1

What is this 8pin cable?
looks like a video card power cable from a power supply (PCI-E 6 + 2)
too lazy to translate
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