Is everything in IIS 7 configurable with the web.config? Is there anything that can't be configured with web.config?
I am using IIS Express and am can't figure out how to do some of the configurations I can do in IIS 7 because I don't have the GUI to configure things.
No, there will be a lot of things that cannot be configure in web.config, such as bindings, permissions, logging, etc.
Try this for an option on how to configure : IIS Express Configuration