I can see this gets asked a lot however after many hours of reading I still don’t think I know enough to settle on something so I’ll explain my specific situation as best I can and see if anyone has advice I can use. 
This house has a few items.
MacBook Pro (late 2010) with Sierra (MacOS) - this is the main computer as it’s stationary on the wall and plugs directly into a Sony Smart TV (from 2012). For a long time this was the main media server as well. It has a Mac backup drive.
FreeNAS 9.2.0 box which is on it’s way out. Intel, 8GB Ram.
FreeNAS 11 box which has finally convinced me that FreeNAS is just not the solution for me. 16GB Ram, AMD quad core something or other.
Windows 7 Ultimate Desktop which is the gaming rig.
There are two more Windows 7 laptops and a Windows 10/OpenSUSE/TailsOS multi-boot laptop. There is also another gaming rig desktop incoming but let’s avoid that for now.
I have another half dozen older desktop boxes I may use somehow or just recycle.
Too many little dinky devices like phones, tablets, but there is a Samsung Smart Blu-Ray Player that has a Plex app.
All of this connects to a crappy Buffalo DD-WRT router I wish I’d never invested in.
The usage - I need somewhere as data backup and to use Plex Pass (PMS). That’s it.
99% of the PMS usage will be on the home network however I’m toying with the idea of allowing an elderly couple to access it remotely from an android box or smart tv so they can enjoy some of my media in their final days.
So, the question is whether I take one of my FreeNAS boxes and turn the into another solution like Ubuntu, OpenSUSE server, Linux Mint, or something else OR can I just buy a large HUB and attach it to the MacBook and run PMS? I really don’t know what to do at this point and am open to suggestions. If the particular hardware is important, I can get that info except the FN11 box for which I’m just not sure other than it’s a quad core AMD with 16 GB ram. I’m not exactly finished with FreeNAS, it just doesn’t seem to be the best PMS solution.
As far as knowledge, I have cursory knowledge of Linux/BSD from a casual POV and Cybersecurity (which to be fair requires less knowledge than trying to have fun - Cybersecurity seems to just ignore errors a lot of the time - like FreeNAS which seems to always pour out errors regardless of where I see it installed). While I enjoy trying out new things, at this point I just want an easy reliable solution that will hold data and allow me to use PMS either on old hardware or a hub.
Thanks for your help.