Backing up projects to separate drives

Folks,
As we work through the switch from Legacy 7 to X...

We've have a 40 minute project -- half done by one editor on his laptop -- half by another on his and both working in FCP X.
Each has kept a dedicated backup drive updated after each edit session.

We are wondering -- if one editor needs to work on the other's material from either of those backup drives -- are there relinking issues with X because a different computer is being used?

That's one question -- and here's another related, but different scenario:
Assuming we both possess all the raw files, can we upload a 'library' to dropbox and have the other editor DL and work -- in the same way we uploaded Legacy 7 project files using Dropbox?

Driving all of this -- we tried to upload a library and ran into all sorts of issues...

Thank you,
JR