Take a fresh, empty system (a VM if you lack hardware); restore data from backups to it; check if you can do your work.
It may be that your projects folder really is backed up, but that it relies on some stuff that is outside the folder for whatever reason - for example, a data file that didn't fit in dropbox, or some changes to config files outside the folder (where noone remembers exactly what needed to be changed); or a connection that relies on a private key that's on your computer, gets used automagically, but is not backed up.
I mean, it's probably overkill in your case - most likely your project source is quite safe; but for a working production system it's an entirely another matter.
It may be that your projects folder really is backed up, but that it relies on some stuff that is outside the folder for whatever reason - for example, a data file that didn't fit in dropbox, or some changes to config files outside the folder (where noone remembers exactly what needed to be changed); or a connection that relies on a private key that's on your computer, gets used automagically, but is not backed up.
I mean, it's probably overkill in your case - most likely your project source is quite safe; but for a working production system it's an entirely another matter.