First, since GSX Level 2 comes with a Trial, it would have been easier if you just tried it yourself, just install the current GSX installer, which includes all Level 2 files and features, which will work in Trial until purchased.
In any case, GSX passengers can work with all the following configurations:
- SODE jetways. Either provided by the scenery, or by GSX Level 2.
- Passenger stairs+Bus used in aprons
- Passenger stairs "embedded" in the airplane door, with the ability to define them in the GSX airplane configuration editor.