the name crayfish can mean so many different species of crustacean, it is difficult to determine what the rules mean, or what species are in the packet without using scientific names. The supermarket bought ones could be anything from crawdads to a white clawed. Personally, I don't like using cooked prawns, or crayfish tails - it seems a little artificial to me. Completely irrational. I've caught perch, chub and pike on raw prawns, but they are hellish expensive. Some prawns are so big, that a tail would be the same size as a young crayfish. I've free-lined a few large prawn tails on rivers and caught chub, they hit it with a right bang. I'm sure perch would too.
As to the moving question, yes, I'm sure a twitched one would be more attractive. Not moving, just inched occasionally. it also ensures you are in contact - essential for detecting those perch bites before it gets swallowed. I mainly fish rivers, and I've caught perch while retrieving a free-lined worm - they've chased it upstream. Only ever smallish ones though, half a pound or so. Pike too, but that's probably more obvious. I'm not sure about perch behaviour in a stillwater, but no reason to assume any difference. I've caught them on a moving fly in a lake when fishing for trout.
Mike