I use tarballs because it allows me to not trust the backup servers. ssh is set up such that backup server's ssh keys are certified to only run a command that will allow them to run a backup script that will just return the encrypted data, and nothing else.

It's very easy to use spare storage in various places to do backups this way, as ssh, gpg and cron are everywhere, and you don't need to install any complicated backup solutions or trust the backup storage machines much.

All you have to manage centrally is private keys for backup encryption, and CA for signing the ssh keys + some occasional monitoring/tests.

One up for rclone, it's parallel and supports many endpoints.

Can't you add only changes to a tar?

Indeed it does; see the --listed-incremental and --incremental options:

https://www.gnu.org/software/tar/manual/tar.html#Incremental...