I have a project that is in total, about 2TB in size (all raw footage included). What is the best way to back up the project to a second drive? Should I do the 'duplicate project' option in Final Cut? Or will dragging and dropping Finder work fine?
Yes, use FCPX to move (or copy) your Events/Projects. If choosing to duplicate (and not move) and your media is alaised in the Event, you will need to "Organize" on the new hard rive and bring the media over to the new hard drive.
For Raw Footage and other elements that aren't controlled directly by FCPX, you can use the Finder or a file copier with verification, like ShotPut Pro.