I putty-d in and went to NPM Manager > S (System Maintenance) > L (NPM Backup) and had both Lan Backup using FTP and Lan Backup using MS Networking configured.
The MS Networking mirrors what is configured in the Web setup. The other .tar must be the FTP.
Is either one more desirable to have than the other? The .tgz simply contains another .tar of similar, but not exact size as the FTP Backup.
These are Linux archive formats... TAR is an uncompressed archive (or archived with 'compress' using the -Z option), a single file containing a collection of files and directories. A TGZ file is a TAR file compressed with gzip which is a open source compression-only tool (it doesn't archive multiple files itself) with greater compression than ZIP often used in Linux environment.
Compress is highly inefficient and only does marginal compression but is very effective with text files, and has very low processing requirements, it was introduced and used typically in the 1980's. Gzip is much more efficient and does very good compression with all types of files but is more resource intensive, it was developed and used mainly in the 1990's. In practical use, although gzip is still fairly common, bzip (2000's) and xz (2010's) are much more effective at compression, resource use, error checking, and error correction, but don't see these last 2 used much in Mitel's Linux servers.
So in theory, depending on content, a TGZ will contain the exact same information but be a much smaller file. A TGZ file will also have CRC integrity checking where a TAR file does not have any integrity checking. There is no reason to use TAR over TGZ except for speed.
The difference between a TAR format archive and TGZ's internal TAR file in this case is that the TAR archive file by itself is using the 'compress' option and when it is used with gzip to make a TGZ archive, compress is not used prior to processing through gzip. The information is still the same.
Hope that makes sense...