Yes, synology has its own Raid5 blend that is really good. That's enough. The 218+ is a little faster and has more functions (because it's intel and not an arm chip). But for music/photo it doesn't matter, with the 418 there is more space for hard drives: only one thing, a Nas is not a definitely secure backup (e.g. currently against ransomware only conditionally) - therefore always an offline backup. If you both have a synology, you can also both back up remotely, e.g. weekly).

I bought the NAS for music, photos and documents. Time Machine was also added and I still have a webserver with php and mysql running. The NAS is absolutely up to the task and runs without any problems. I would also recommend RAID 1. Since a hard drive died on me 20 years ago, all my mass storage devices run in RAID 1.
In my opinion, one thing to consider is that if you are sensitive to noise, you should not place the unit in the living room. But that is the case with almost all NAS.

... with RAID1, he would of course need larger disks. The DS218+ with 10 TB Seagates would therefore also be a consideration.