I have a 17,1 iMac / 3.3GHz Intel Core i5 / USB 2.0 hub / USB 3.0 Bus. I want to buy a 128 usb flash stick for added backups of music, movies, etc. I daily backup the iMac w CCC and a 1TB drive. I want to match a new USB stick to the iMac. Should the new stick be USB 2.0, 3.0, 3.1, or does it matter with the above iMac ports?