I have a tech illiterate mother in law who I switched to Zorin OS (an Ubuntu fork).
I installed a wireguard VPN client on her laptop and did drills over the course of 3 days to make sure that she understood how to connect. Anytime she needs help, I can tunnel through my wireguard server and log on with my own account - Heck, as long as she doesn’t change her password, I can log on as her as well.
That has made remote troubleshooting significantly easier as she is located about a a 23-hour drive away.
I would get multiple drives and do RAID. Here’s a helpful calculator to figure out drive quantity, size, and configuration. The reason to do RAID is redundancy. Hard drives will fail (even NAS branded drives). You do not want your photos, media, etc to be lost in that case. I personally do not go with anything below RAID5 (and for super sensitive things, I’ll even go RAID6 - despite the hit on overall capacity. If the optiplex has drive capacity for multiple drives, I strongly recommend you go this route.