answering question #1:
There's a section in Help about saving and backing up projects. Just saving a project doesn't package up the source files that a project refers to. The last line of that page about saving and backing up projects refers to a feature with which you can also back up and collect the assets used in a composition or project:Collect Files.
Comp. 792 wrote:
Is this a common workflow to save the image sequence as a movie file first, then import it into a composition rather than just importing the sequence directly into a composition?
It depends. There is no general advantage in using movie clips as long as you have sufficient disk space to retain the image files. It may even slow down things as some CoDecs are less ideal for out-of-sequence access to frames, especially compressed ones. You also enter the danger zone, when one of the clips gets damaged. It may be unusable, while on the other hand it would be simple to fix a still image by re-rendering it from your 3D program our touching it up in Photoshop. As a last thing of course you have to consider, that most movie formats are just 8bit or 10bit and you will lose color fidelity when working with scanned film frames or, again, 3D rendered images. In the latter case this can even be expanded upon, as only image formats support full 32bpc at this point and formats like RPF, IFF and OpenEXR are the only ones to hold additional buffers like depth or object ID. Some movie formats don't even support Alpha channels... It realy comes down to the kind of work you do. I only use movie clips, if they originated as such from editing programs, when there is a considerable saving in disk space or when I have to send it to otehr people to avoid mess ups. For my personal workflows I prefer to keep the original image files around aslong as I can, which, given todays cheap pricing even on terabyt harddrives is not really a problem.