3-2-1 means 3 copies total on 2 different media with 1 copy off-site. An easy way to implement would be make a local copy outside of your NAS/RAID(different NAS or external HDD) and create a copy of that somewhere in the cloud or hosting(backblaze for example)

You should probably not look at your whole storage when thinking about Backup, but create different logical pools. For example I have 3 pools: media files, personal files&photos, app config files for my docker.

I don’t backup the media files because I can reacquire them, I have a very strict backup policy for my personal files and a more relaxed policy for my config files.

I use duplicacy to manage a local copy and a cloud copy and do restore tests sometimes. Duplicacy can also manage retention of its snapshots so I can keep years old versions of my personal files but only a few weeks worth of config