English Cockers aren't as energetic as a lot of spaniels, but they can still be very energetic at times. Walking politely on lead and not running off is all in training. Any dog will pull on the leash if not trained otherwise, and most dogs will run off (especially spaniels and hounds, in my experience, as their nose often gets the better of them). Your friends' Cockers might be different when you're around vs. when they're just with their family. Perhaps a Cavalier King Charles Spaniel would be good? They can have a lot of health issues, so you'd have to be sure to get one from a reputable breeder, but I think they fit your needs pretty good. I'm not sure at this moment what else I'd recommend, but I'll think about it and come back. Only you and your family will really know what's best, and if you feel the English Cocker is, then I highly encourage you to spend time with some (besides your friend's) and just see for sure if they're the dog for you.