I haven’t used restic, but it’s on my radar. Supposedly it works best with minio, a diy s3 bucket server.
I personally just rsync the entire /, then take a snapshot on my backend storage. On next rsync, I only do incremental on top of the existing backup and delete what was removed on target, but still keep the original data in the snapshot. That way I always have “full backups” that only take the space of incremental backups. If I had zfs on both source and target, I’d just zfs send.
If my system crashes, I reformat a drive, copy the previous data, chroot into the environment, then reinstall the bootloader and whatever else I need to make the system startable (like modifying the partition ids in fstab if I have new partitions on which I copy the data). It’s not too difficult if you know what you’re doing, but takes a bit to get used to it.
The reason I learned how to do this, was because I was forced to move people from a slightly larger linux partition, over to something a bit smaller (still 256gb drives, but moved to lvm with separate root and home volumes, kinda needed to be able to unpack to a differently configured partition, rather than clone via clonezilla like usual).
Speaking of clonezilla, I stopped using it when I discovered that I could just pipe dd into ssh into bzip2 / gzip / xz / zstd / <insert-compression-algo-here>. That way, I don’t need to have a clonezilla iso or usb around, I can just boot whatever linux distro I happen to have available on hand. It would go something like:
dd bs=4M if=/dev/sda status=progress | bzip -9 -c | ssh user@server "dd of=/home/user/backup.img.xz
Or if you want it on local disk, just bzip -9 -c > /path/to/backup.img.gz, instead of piping to ssh.
I would suggest against syncing files between linux and windows, but if you really want to, syncthing is ok. I haven’t used it in ages though (I used to have it sync linux, windows and android keepass db). I prefer having things in one place, makes me less prone to edit in multiple places.