Question

I'm using a MacPro 2 x 2.4 GHz Quad-Core Intel Xeon, OSX Version 10.11.6.

Since my mac does not have USB 3 connectors, I have to use 2.0.

Answer 1

From Page 5 in the User Guide:

The second comment you made is correct, the older Mac Pro's do not have USB 3 connectors. Your performance will not be affected by using a USB 2.0 cable.