Javelin:
There as as many ways of doing a managed descent as there are doing a selected descent to meet the profile you desire, there is no limitation to select speed in managed descent or eventually if necessary(but defeating th purpose of fuel savings) the use of speed brakes or early configuration, while assuring yourself of at least altitude constraint compliance.
I leave "playing with the machine" to test pilots without passengers, with flight test engineers and data gathering to tell me what the ACTUAL more efficient way of flying the aircraft is, not the PERCIEVED one.
You might be a highly skilled pilot that finds that "striking a balance between ultimate economy and professional experimentation provides hours of endless pleasure and enables me to outwit our technical officer time and time again" is the proper way of flying, but myself as more limited pilot, will stick to sops and keep flying the airplane like the people who designed it and tested it recomend that I do, in my case Airbus sop's.
G