I’m a +1 on this. A secondhand Synology set up with some RAID will delay this decision for a few years and give you time to build your expertise on the other aspects without worrying much about data security. It’s a pity that you’re nearly at the limit of 8TB - otherwise I would have suggested a two bay NAS with 2x8TB, but if you’re going to use second hand drives (I do because I’m confident of my backup systems) maybe 4x6TB is better. Bigger drives are harder to come by 2nd hand - and plenty of people will not be comfortable with secondhand spinning rust anyway - if that’s you, then a 2 bay with 2x12TB might be a good choice.

The main downside (according to me) of a Synology is no ZFS, but that didn’t bother me until I was two years in and the owner of three of them.