The discovery cable channel had a great doc on the propulsion system on the QM2.
Very interesting and it did lean a bit to the technical side of things. Worth looking at if (and it will) it comes around again.
The good thing about podded propulsion is there is no shaft alignment , therefore engines can be laid out better. The QM2 has gas turbines on the funnel deck, coupled to alternators, for booster engines. These are simply wired into the pods. You can also get 360 degree propulsion from them. The fixed pods are aft, but the propeller faces into the water. This gives much more efficiency, as the full face of the prop is presented to the water
A slight clarification to your post Moaf. QM 2 has four Wärtsilä 16V46C diesel engines, each driving an ABB alternator with an output of 16,800 kW and two General Electric (USA) LM25000+ gas turbines each driving a Brush alternator with an output of 25,000 kW. The total 117,200 kW power capacity is connected to the main switchboard and alternators are brought on line as required to meet variations in the combined propulsion and hotel demand.
This power station concept has been used in the design of new cruise ships for more than 15 years. The major advantage is that the engines in use at any one time are operating within their optimum power range. There is also greater flexibility in the location of the machinery spaces. As you state Moaf, in the QM 2 the gas turbines are located in the base of the funnel housing.
The QM 2 has four Alstom/Kamawa Mermaid propulsion pods, each having an output of 21,500 kW. The arrangement is that the forward pair are outboard and fixed each side of the central skeg. The after pair are inboard, astern of the skeg and capable of azimuthing through 360 degrees. All face forward to enable the propellers to bite into clear undisturbed water. The propellers are about 20 feet in diameter with bolt-on, fixed, stainless steel blades. There are no rudders or stern thrusters, but she has three Rolls-Royce Kamawa bow thrusters, each of 1,500 kW output.
The attached pic and those that I have placed in the Machinery gallery are from the Cunard commemorative book and the special RINA book on the building of the QM 2.