There isn't any real difference other than the name. All a control valve can do is close and open by a certain amount, thereby increasing or decreasing the pressure drop across the valve when flow is present. That's it. What causes it to close or open is dependant on its control feed or feeds. In you case they all seem to be pressure related, but it could just as easily be flow, level, temperature or any other variable, sometimes lots of variables and the control system picks the worst one to control on. Each process will require a different thing or things for the valve system to control on.
does this answer your question?
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Also: There's usually a good reason why everyone does it that way