One question about GSX is the reason I don't see passengers loading is because I am using the Jetways?
Passengers will use jetways, but they MUST be SODE, they won't show on default jetways ( I think you saw a message about this ). The jetway can either be SODE jetways provided by the scenery itself, or SODE jetways that has been replaced by GSX.
GSX will replace all default jetways on the default scenery automatically with its own GSX/SODE version, but on 3rd party sceneries that don't use SODE jetways, the replacement is not automatic, you must first follow a specific procedure to exclude the original jetways first, then add GSX ones. Explained in the manual, and there are a couple of video tutorials on this forum too.
We don't have any plans to support X-Plane for the foreseeable future, mostly because, with the workload required to support FSX:SE, P3D and the upcoming MSFS, we simply don't have time to follow another sim.