Someone on github has a decent comparison of a bunch of different backup solutions. Afaik Kopia generally uses more memory but is the faster, and restic is pretty fast and doesn't use as much RAM as kopia (for awhile people recommended against restic as it lacked compression, but they added it in 0.14 last year).
https://github.com/deajan/backup-bench#in-depth-comparison-of-backup-solutions
I personally prefer kopia (has a gui to help configure it), but restic is also good. I'm not a fan of Borg because you can't backup directly to object storage (eg. Backblaze B2/Amazon S3/Wasabi/etc), you have to backup to a local or mounted drive, then upload the backup.
I'm also waiting on https://github.com/rustic-rs/rustic to get better windows support, as it should use less memory than restic while being as fast, or maybe even faster.
No. Previously if you used unreal but didn't ship any engine code to end users you didn't have to pay anything (games obviously ship engine code, so they're already paying once they pass a certain revenue threshold or upfront if they want a support contract, and the announced pricing changes explicitly don't effect games)
Unreal has been pushing hard into film and virtual production workloads, but they weren't getting paid anything due to the existing license terms.
Now if eg. you're using a virtual set (like the Mandalorian) or doing in camera previs (basically previewing approximately what a scene will look like with CGI, either between takes or even viewing it live on a second monitor attached to the camera as you film) with unreal you'll have to actually pay.