Backblaze and Crashplan are two options that have come up, anything else? I’m ruling out Dropbox/OneDrive/iCloud since I want one-way sync (lots of heavy audio files that I work on extensively)
I find that most data is better kept elsewhere (bookmarks in browser sync tools, email and contacts with email provider, personal documents in cloud providers, multimedia - yes, copied to multiple external drives or a NAS, S3 - maybe write a script and schedule it).
I used Arq Backup for about a year and while I liked the idea, the UI is absolutely awful and the restores were painfully slow. It’s way too hard to control the backup behavior to do what you want. I didn’t feel like I could trust that the data was going to be reliably restored.
For system migrations, I just use target disk mode to go from old Mac to new with the migration assistant, which is also stupidly fast between Thunderbolt 3 SSD Macs if you’re using a proper cable (300MB/second for me). Very nice for when you want to satisfy your new computer excitement.
I feel that time machine has the same utility, or to provide backups to non-technical users who either refuse the cloud or don’t know how to work a file manager (or both).
This could be a pain but depending on your needs: an often forgotten option to look into is Blu-ray Discs. They could be a nice option especially for redundant long term storage and the price per gigabyte is very low.
So I have several USB3 external hard drives which I backup to in rotation, more or less the same sequence as we used to do with LTO tapes. On Apple Macs I use TimeMachine and on the Linux servers some custom scripts which basically achieve the same result.
Of course, the backup scripts exclude temporary and other non-essential files. The other key factor is to monitor drive errors and being aware of the MTBF of disk drives and replace them before they become unreliable.
However, you might have more files than I have, so DVDs might not be suitable for you. See how many files you have so that you can see how many DVDs you would need, and then you can see if it is suitable for you or not.
I have also used Backblaze before, works the same way with rclone.