Another late comer to the party, sounds like you are on the right track here. I've had a library of FLAC files on my server for years and also transport those files to a DAC hooked up to vintage gear. A bunh of random thoughts that might help.
Avoid USB. Avoid MS/apple solutions. FreeNAS (or in my case ZFS on Solaris based OS) is the best way to go, very stable and no corporate monopolies spying on you/sending data off your network.
WD Reds are a great choice, designed for 24/7 use is true, but the best part is they are designed to spin-down when not in use and therefore save power as well as longevity
My FLAC library is over 30,000 songs and uses less than a TB of storage space. For a music only server, a
PAIR of WD Reds
mirrored is a good solution. Never used freeNAS but I do know it has ZFS which I use on my server as well. ZFS is very configurable with different RAID layouts possible. Using ZFS' RAID-Z2 capability I have never had to do a backup and never lost any data. In a mirrored solution, both drives would have to die to lose data. In a RAID-Z1 solution you'd have to lose two out of five drives to lose data and the number is higher for RAID-Z2. There is also the consideration of expansion/upgrades. My initial setup had 5 1TB drives. Worked great for about a year then 2TB drives became affordable. With ZFS there was no need to backup the data and recreate the pool with new 2TB drives. ZFS allows you to simply replace each 1TB drive with a 2TB drive (one at a time) and after you replace the last drive the pool is now resized to to capacity of your 5 2TB drives. You can also just add a group of drives to an existing pool to increase capacity as well. I'm a ZFS fanboy as you can tell, been using it on my home server since 2009. Never let me down.
Your home NAS server should be able to share your music/videos filesystems using SMB/CIFS, NFS and DLNA. Once that is setup, EVERYTHING in your house including cell phones can see the files on your local network. For example, I have a TV in the guest bedroom hooked up to a cheap LG bluray player with wifi built in. That can even see my movies because it supports DLNA. I can play movies/music on my phone with VLC because it supports DLNA.
I'm also a big fan of the Raspberry PI 3B+ (built-in wifi) for any kid of transport. Reason being, they are cheap, the software for them is free and the best part is there is always an app on the play store for control of whatever software you install on them.
For stereo music to a DAC and then to a vintage receiver the RPI will need a digital coax out HAT board as well (Hifiberry makes one for around $40 and ALLO makes a great one called the digione for about $100). If you don't have a DAC both those companies also make HATs with a built-in DAC. If you aren't going to run LMS, volumio worked well for me, it has a free phone app as well. When using LMS, I use Orange Squeeze.
For connecting to a TV it's simply a matter of installing OSMC on an SD card, hooking up an HDMI cable to the TV and setting up OSMC to tell it where the home file server stores the video share. Then go get 'Yatse' from the play store and done.
Two more points, one: the WAF for just having to use a cell phone app to control music or movies is very good (at least in my home). The second point is there is no greater feeling in the world than going to the high-end audio store with your wife and her seeing a $15,000 streamer/transport and asking you 'isn't that what we have at home only cheaper?'. Yes honey, wayyyyyyyyyy cheaper.