1- Which one do you use?
Depends on what do you want. Generally, General sceneario is just great and suficient. If you want to custom a lot, Two Classes scenario could give you what you want.
2- under SD.Tasks.Adapter.Webservices.SchemaImporter, why are all the options grayed out?
That are grayed out because there are just there for backwards compatibility. Please read the manual (Distributed systems) to know if you need to enable them.