Backing up Files of the current System before Migration

While I did love my time with garuda KDE, I would like to switch to BSPWM on an another operating system (Arch BAREBONES ofc) and I would like to keep my files.

What would be a good way to make the files of my current system can be transferred over? Like Can i mount the same root directory while reinstalling or how do we go about that?

Furthermore, I would also like to backup my entire OS, just in case stuff goes down. Would ARch ISO be a good tool ?

Given you're moving to Arch it will be worth getting used to the Arch wiki: