Do I reinstall the whole system, install Pika, point it at its old backup folder and have it restore? If so, what does it actually restore? Does it originally back up apps, their data and whatever I have in my home folder, then it restores all of that to the new system? Or does it only back my config files and home folder?
Pika backup is made for backing up files, rather than a full system. By default it only includes your home folder, and excludes things like cache folders. Per their Github: “Pika Backup is designed to save your personal data and does not support complete system recovery.”
The file restoration feature is more like plugging in a USB drive with files stored on it. Pika backup mounts your backup as if it were an external drive, then allows you to copy your files from it.
You might want to consider a system backup tool like Timeshift instead. That seems like a closer match for what you’re describing.
Pika is slightly different in how it stores data (since it does incremental backups, can do encryption, etc.) but as far as restoring data is concerned it’s pretty much the same as copying files to a different drive.
I haven’t used Timeshift for a while. On closer inspection they do say “Timeshift is designed to protect system files and settings. It is NOT a backup tool and is not meant to protect user data.”
So I guess it’s the opposite of Pika. Timeshift backs up your system, Pika backs up your user data.
Timeshift can do both if you want it to though, by going into Users tab and selecting Include Everything, then removing any Filters.
I haven’t used Timeshift to restore data, but going by their Github page it looks like it restores everything to where it was before. So the restore process (in case your OS drive dies, for instance) might be to install your OS, install Timeshift, then select Restore. It’ll restore your previous user, settings, etc. Then you reboot for the restored data to appear.