FreeBSD
AllTheModzAreCancer
All you have to do is plug in the new router and use the app to update the MAC address. I did it a couple weeks ago.
WD Gold 10TB but I miss the HGST Ultrastar days (before WD got them) HGST added something when they took IBM's disk drive business, but something was lost when WD acquired them.
I'm a noob too, but I can tell you that you need to keep in mind the purpose of your NAS. Ask yourself this: am I storing archives that will probably not be accessed much, or am I hosting a filesharing service or streaming or something else that will need a bigger cache and more RPMs? Also try to prioritize CMR over SMR.
When I built my NAS 3 years ago I bought a used SuperMicro MB, a used Xeon CPU, used ECC RAM, and it's still going strong. My WD Gold drives were new of course, but you can find some good deals on used drives too. Just make sure that you take into account not only the hours on the drive but reads, writes, and stop/starts too. Also look at the seller's rep to see if they have a history of reprogramming the ROM to show a false SMART.
Hopefully you are using SMR ram and a ZFS filesystem. TrueNAS is a great OS that uses openZFS and RAIDZ. If you are using lower-end or used NAS drives then consider using more parity drives than if you were to use new, enterprise quality drives.
The premise of the question is to open a discussion about software that lives in a de facto state of being completely open source.
As opposed to asking whom on a hodgepodge full of strangers?
As opposed to not opening a discussion where erroneous information is not brought to attention...