Which Synology for off-site backup?

Hi all, I have a Synology DS920+ mainly for family photos and stuff, only has 2x 8tb disks in SHR and in thinking of adding another Synology in my mom's house as an off site backup. Thinking of a DS223J with 1x 8tb disk. I'm thinking since it's just an off site backup I won't be needing the benefits of RAID as if anything were to happen to that, I still have 2 disks with the data in my main NAS. With this if I decide to expand my main NAS in the future with 2 more disks, I can add 1 disk to the ds223j to cover for that.

What do you guys think?

Thanks!