I know Plone uses the data.fs and possibly some external file system; however, what i remember is if you don't configure to use external files, all data are stored in the data.fs Is this correct?
Am i safe in using collective.recipe to only backup the data.fs?
Yes and no. There's the filestorage with data.fs and blobstorage. The blobstorage contains larger elements such as images, so you'd need to back it up as well.
Also my post here Cookiecutter zope instance and ZEO - #10 by Esoth where I use cookiecutter as a sort of replacement for setting up config files and then use to create a script, somewhat analogous to what collective.recipe.backup was doing with buildout