What do I backup and where?

I back up everything. I have a lot of time and memories invested in the data that I have curated over the years, and I have been bitten badly once, and lost a massive amount of data. Now I’m self-hosting I want to make sure that everything is backed up somehow, somewhere. I use the Yunohost backup with a cron job for automatic back up to a USB drive and and Restic for a more granular, selective backup. I'll do a section later just on Restic and how I have set it up.
So I have the following in place:
A USB keyring that has the latest version of the Yunohost image. In the event of a total disaster, one that requires a complete rebuild, I can boot from the USB keyring and restore the system. I have a small wired keyboard and a tiny 8-inch monitor so I can do the necessary... I check every few months with the Yunohost website and grab the latest image and update the keyring. Every six months I plug everything up, the keyboard, monitor and boot from the keyring, just to make sure it all works. well you never know...
Two 2TB USB drives for backing up to. (Old fashioned spinners!)
One drive is labelled "YNHRECOVERY". This is where my server does its backup using my cron job from earlier.
The other is labeled "DATARECOVERY" Using Restic I copy the latest backup from the YNHRECOVERY to this drive, so now I have two copies of the full server on two separate drives.
An iDrive S3 account where I have three buckets.
ynh-idrive-s3: This is my yunohost offsite backup
my_laptop: I use Restic on my Mac and back up the whole of the home folder, with exclusions like the Library folder and a few other, like .Trash.
h_laptop: My partners laptop, which is a Mac gets the same backup.
1. Symbolically linked to store all the Yunohost backups that are created from my cron job.
2. A backup of the mega important stuff using Restic. More on this one later. What does mega mean? This is a personal choice thing. Yes, it's all important, but gun to the head, what's really important given what you have at your disposal?