remote site client deduplication with fingerprint seeding

To answer your questions in order:

1) Yes you can copy the files to a USB, ship that to your central site, attach it to an appropriate client, back up the folders in a special backup job, and then point the remote client to that image. You would use the pd.conf method outlined in this technote: https://support.symantec.com/en_US/article.TECH144437.html This technote has both option you are asking about. however they have their individual issues.

2) This would only work if you are backing up to a deduplication pool using the client side deduplication.

3) As I said before both processes have their strengths and weaknesses. The pd.conf method calls for either a copy of all the machines being sent to the central location or hoping that a few of the images would be enough to help with deduplication. If you use the seedutil tool you once again need to find an image that would have the best chance to deduplicate but is faster to configure for multiple clients.

Whichever method you chose read the technote carefully because there are different variations to the methods depending on the version of NBU you are running. Also what is missed is the need to turn on client side deduplication through Host Properties of  the master server. It is off by default.