It can be whatever you want, if you want it only for documents the disks don't need to be to large, it can even be NAS SSDs (depending your backup model), but considering the office apps requirement I also think synology is a good option.

Because is not like the previous digital version, now they are the same but there is an option that includes the CD Drive and one that doesn't include it but can be purchased separately in the future (digital version)

There is also Synology photos and I like it but see a lot of people recommending immich, someone that has used both know if there is notable difference or benefits?