Are SATA cables differentiated by speed levels?

The three speed levels for SATA devices are SATA, which allows up to 1.5 GB/s, SATA II, which allows up to 3 GB/s, and SATA III, which allows for up to 6 GB/s.

Does SATA III device require a SATA III cable to support the higher transfer speed?

You can use a SATA I or SATA II for SATA III devices, although we recommend pairing a SATA III cable with SATA III devices to ensure the desired transfer rate whenever possible.

What is the difference between a straight SATA cable and a 90-degree or 270-degree cable?

The only difference between SATA cables that have two straight ends and SATA cables with one end at a 90-degree angle is the ease or difficulty you'll experience in connecting the cables, given your hardware set up.