Then, what is the best or recommended way to create a back up of Work in an external USB drive?
There's no generic best way.
If you format in a native MOS filesystem like FFS, SFS or PFS, you won't be able to access them on anything but MorphOS or an Amiga. Those kernel modules on Linux are now old and deprecated. If the worst happens and you no longer have access to MorphOS or Amiga, it'll be a battle to get them back. But as pointed out, it's the only
way of preserving Amiga file attributes and file comments.
If you format in NTFS or exFAT, performance on a non-Windows machines will be poor and/or limited. And there will be no way for you to fix corrupted volumes except on a Windows machine. I've always thought NTFS was awful for removable drives and seems to suffer from all sorts of corruption and file permissions issues when used for that. exFAT was supposed to fix that but instead became the black sheep, poorly supported by everyone.
If you format in EXT3/EXT4, performance on non-Linux/BSD systems will be poor and/or limited. And you will need Linux to repair corrupted volumes.
FAT is probably the best all-rounder and compatible everywhere but has the filename length, partition size and file restrictions many find unacceptable. And you'll STILL need a Windows machine to fix problems.[ Edited by KennyR 26.08.2018 - 22:08 ]