Want to clone a drive to an external device

I’m upgrading my system from Zorin OS 16.3 to 17 (Unbuntu based OS). Before I do, just to be safe I want to use the clone option in Etcher to to clone my PC drive (512 Gb) to an external HD via USB (1 Tb). The purpose is that if something goes sideways with the upgrade I can clone the external HD back to my PC and restore my data, applications and the original OS.
Can Etcher do this? Is there any other steps or precautions I need to take? Shoul I partition the external HD so that it is 512 Gb like my HD on my PC?

Thanks in advance,