I think hyoeractive is the wrong term to use. Show Cockers are heavier built have slightly shorter legs - or they look that way because of the much heavier coat they have over the working cocker. Working cockers do tend to need more exercise and mental stimulation than a show type - but show type are also very intelligent dogs. They can both get troublesome if they don't get enough exercise, both mental and physical.
The working Cocker does look more like a working dog - a bit like a slightly built smaller springer. They don't have such pendulus ears as show type Cockers.
Show type cockers are much more readily available than working and are the victim of puppy farm type breeding. As with all dogs, whichever you choose - if you are looking for one - choose your breeder carefully.
HERE are some working Cockers
HERE are show type cockers
hth
Pam n the boys