I have been using a Synology-based NAS as my main file server for a number of years. It worked pretty well. It was reliable and easy to use.
I particularly liked how it connected to Google Drive and/or Dropbox to synchronise files. That made sharing things pretty straightforward.
But Synology boxes have a tendency to be underpowered and rather expensive it you want a lot of power (and I did).
So, I thought I would try FreeNAS, a ZFS-based system running on top of FreeBSD (rather than some rather proprietary version of Linux on the Synology).
I had a box I could run it on, but I soon found I needed to upgrade it from 8Gb to 16Gb. It was a little too tight memorywise.
FreeNAS is a much more commercial system. By that I mean it is geared towards 'production' use, rather than home use (which was the case with the Synology really). So, the system is very powerful, but a little less easy to use. Actually, there is definitely a bit of a learning curve (and I've been using FreeBSD for many, many years).
I'm using a similar backing up system (off-site with
rsync), but I also use
syncthing to move date (in kind of real time) between the various systems I have at home and at work.
Syncthing works well, although there have been a couple of times (during the set-up) where I got conflicts and resolved them the wrong way (keeping an older version of a file, rather than the newer version. However, that seems to be behind me now.
So, far, so happy (and that's after about 2 months of use).