Suitable 4 bay nas for my use patterns?

I have one Netgear NV+v2 (4x 3Tb) which is unreliable (it just lost 4TB of data); I also have 2 Netgear Readynas 214 (4x 4Tb), which are getting VERY full. So I need (at least) another 4 bay (or more) to fill up with 4Tb WD Red (CMR, not SMR), unless adviced otherwise (Netgear always recommended WD Red, and THB I had some issue with Seagates).
At moment I cannot see the RN 214 any more "in stock" on the UK market, only the 424 (@~£340/370, which in your review, you do NOT really recommend for home use.
I REALLY like Netgear build quality, but I find the software quite user unfriendly - it's designed for the "office network manager" and I am not one of them (although being reasonably computer literate, I analysed data with spreadsheets for 25y). But I also had (software?) problem with the NV+, and a RN104 died on me (but the disks went into a 214 without loss of data, which would have been DIABOLICAL)
QNAP & Sinology have a pletora of models, and quite frankly I don't know where to start.

I need NASses (or other alternatives, not yet considered) to
a) keep all my data safe in one place, in 25 Y I had many PCs & laptops, I need a COMMON storage place; that includes 25 years of pictures, music, live gigs etc.
b) I DL movies series (BBC4, Montalbano, Horizon, F1, MotoGP etc) and lots of other stuff of and I can see with DLNA on the android TV;
c) being Italian, I would wish to have access to the data from Italy. That should be possible with the existing NETGEAR kits, but I never really managed to sort it out; and with my old internet plan (700kb/1Mb upload), and a flaky connectivity in italy, it would have been almost pointless.
d) I never used PLEX, I barely know what it is, I might do in future...maybe. Ditto for NETFLIX
e) I don't have any surveillance in place - it would be useful for sure, but I don't see it happening at moment
f) VERY BAD OF ME - I don't have a Backup policy in place: being very messy, I have lots of spare copies of important stuff, but I need to address this. But with 15/20Tb of unique data (on RAID..5.. ?), that may mean a lot more shopping to do.
Sorry for the verbosity, and thanks for the help in advance - Kind regards

I would suggest Synology NAS. It is very easy to set up and use. They also have the best Windows backup option and also come with a Dropbox-like alternative called Synology Drive.You can also use the Moments app to backup your phone multimedia and also install Surveillance and get notifications on your phone.I would look at multi LAN options such as 20+ series NAS. They have 2 / 4 / 5 bays models available.Their DS Video app will allow you to stream all videos across the internet. They also come with a transcoding function that will convert video into a smaller size so that broadband speed can cope with it.You can also access your multimedia and other files locally via DLNA protocol or another way of connecting.I hope this helps.