your correct, the way the industry is playing the cable id, the higher the number (5,6,7) the higher the capability specs. Thus, CAT7 should logically be a better cable than CAT6A (the latest til cat7 showed up).
However, unless your running high speed servers your typical/affordable computer (desk or lap top) or I-phones can't push a full Giga-byte of data or otherwise, come close to needing to exceed the specs of the cable. Therefore, for the average joe, there will be little to no difference between using cat5 and cat7.
Your good to go.