Resolved Buying A NAS Server

I am looking to buy a NAS server,This will be my first NAS Server,
I am going to use it for my cloud service and for TV media (cutting the cord)
I want to backup all my files, video, & pictures, and all the cell phones in my family so the can connect remotely over the internet back up stuff on their,
I do not Think I will be working on files directly on the NAS only Storing files their the Updating them Pulling them back to my computer to edit make changes the sending back to the server.
I am to use it a lot for TV media, streaming I am Looking at these Ready made units, I am going to use RAID 1 and 4TB hard drives on 2 Bays

Synology 2 Bay DS216J NAS Diskstation
https://www.amazon.com/dp/B01BNPT1EG/ref=emc_b_5_t
I see this has 512MB memory That worries me is it enough?
Synology 2 Bay DS218J NAS Diskstation Is about the same
Next is
QNAP TS 231p-US
https://www.amazon.com/TS-231P-US-P...8&qid=1531332865&sr=1-1&keywords=qnap+ts-231p
This on has 1GB of memory I like that, and the price More memory that the Synology ds216J and ds218J have.
But then I noticed that the
QNAP TS 251 Has a faster CPU and supports Media Transcoding
Media Transcoding Is this something I need for that will help streaming TV ?
Then this one
QNAP TS 251A
https://www.amazon.com/TS-251A-pers...8&qid=1531333922&sr=1-1&keywords=QNAP+TS-251a

This one has a HDMI port on front

What do you think is the best for a just a home NAS cloud box?
I am new at this NAS Server stuff
Thanks for your time reading this
Your thought will be helpful