Cloud storage is great including Google Photos to hoover up pictures and Microsoft OneDrive for shared files especially MS Office documents. Definitely the best if the free or paid tiers work for you but for me it was going to be too costly. I've been trying other ways like running a file share on an old computer but its too loud and takes too much space or hooking up a USB drive to my Asus RT-AC86U but it's SMB1 and acts weird. So a NAS - a dedicated device that will be compact, quiet, power efficient, feature rich and upgrade-able.
Synology, QNAP, and others make a plethora of products and I rely on Dong Knows Tech and also on write-ups like this one on the whole current Synology + series on NAS Compares. I've used both Synology and Qnap at #dayjob and Synology I think is more for tinkerers and I do like to poke things with sticks..
How big a NAS? It really came down to that I know I will want to upgrade the hard drives in the future so I want the fewest possible and that I can get the capacity I want on a 2 bay unit.
And then the model comparison - if you go on Synology's site and look at their products even limiting to 2-bay models only they have 8 current products. What the great mother of Fridays? It came down to that I will heavily use a NAS and the price differences were relatively small to go right to the DS720+.
Alternatively, for something for backups and basic file sharing, people frequently sell their old NAS on Craigslist / FB Market. I wouldn't buy drives secondhand, they're the only components that routinely fail and every year someone else used them is a year less life they have. Otherwise, yeah buying a NAS second-hand would be great get a couple new drives, awesome.
Time to go check my shipment status again...