What are the different variants of ILS intrumentation?
In the Boeing next-generation "NG" flight decks, the PFD can be configured one of two ways. The first way, is the default presentation, where you only see to top of the HSI. The pilot will fly the aircraft via the pips along the bottom and right of the attitude indication (and usually with the flight director cross as well):



If my memory is correct, Boeing, NASA, and others did a number of human factors studies over the years and found that this layout allowed pilots to more quickly understand critical flight information, and this layout is now standard even in GA glass cockpits (e.g. Garmin G1000, Collins Proline).

The second configuration provides a virtual "six-pack":



This configuration is primarily used for airlines that are transitioning between "Classic" and "NG" flight decks. One airline I remember in particular is Southwest, as they had a combination of 737-300/400 and -700/800 aircraft and having a classic configuration on their new flight decks allowed all of their pilots to fly any of the aircraft, without needing significant differences training. The particular presentation can be customized per the airline's needs. An airline will typically move exclusively to the modern PFD display once all of the older aircraft are moved out of the fleet.