I follow the practice of creating a new folder for each project and changing the four settings (Scratch, Thumbnail, Waveform, Autosave) to the new folder. That way when the project is done, I simply offload the entire folder to my archive drive and free up the space on my main drive. Also, if I am working on multiple projects at once, I can keep files from getting inter mingled. And if I need to come back and work on an old project, I just pull it off the archive and start where I left off.
Is there a way to set these four setting automatically?
I wouldn't worry about waveform, thumbnail, and autosave. The first two will rebuild automatically very quickly, and AS is small enough you wouldn't need to dump those.
As far as Scratch, if you set one main destination for everything, FCP will automatically create a new folder with your project's name. You can then save this folder to whatever drive you choose when archiving. And, if you need to revisit the project, you can quickly reconnect your media to the new location...should only take a minute to do so.