Water-tube boilers and Titanic's engine-room crew

How much would water-tube boilers reduce the engine-room staff on RMS Titanic?

Dramatically, chiefly by removing the need for most of the stokers required by the original coal-fired plant.

Titanic's coal-fired boiler rooms required large numbers of stokers to shovel fuel and tend the machinery. A water-tube arrangement would remove most of that manual coal-handling burden. Some engineering personnel would still be needed, but nowhere near the original stoker complement. The changed plant would also make the liner faster. Propulsion design shapes both crew size and performance.