Part of our work is downloading, uploading and viewing (not editing) large video files. I am also looking for efficiency, fast updates and little downtime for installation. Ok with a bit of overkill.
What am I missing with the DDR4?
As for the reviews, overall they seem ok to me.
I agree with what has been said about the seller by
@Chuchum Ainer and
@DaasTora (insert whatever corny joke you like here). I remember what it was like before resellers plagued places like Amazon, Newegg and Walmart with scams and inaccurate listings. It is sellers like CUK (which was one of the first, agav) that are why I filter out any other sellers except Amazon, particularly for marking upgraded computers as new.
(At the time, I advocated for a new filter setting called "Upgraded" but no one listened to me, not the companies themselves and not the computer magazines I wrote to. In any case, without anyone enforcing accuracy with the filters, having a different filter setting would be useless. )
DDR4 is one example (and the only explicit one) of using a lower spec than is possible to use. I was not saying that DDR4 is not good enough - I was pointing out that most 13th gen i9 systems come with DDR5, but this seller chose to use the cheaper DDR4 (because this computer likely didn't come with an i9 originally). To be explicitly clear: I do not trust this seller to upgrade this computer with parts that are worth the price they are asking. On the contrary: I suspect them of using subpar parts. And this suspicion is based on my experience and not merely on my cynical nature (though I am quite cynical).
On to your usage:
What you describe requires a fast internet connection and maybe a bit more RAM (=16GB). A fast SSD (which this computer might not have) will help if the videos are 4K. An SSD that is large enough to store whatever videos you need at any given time (average 4K video takes up 25GB an hour, so you do the math). A fairly modern i3 (12th gen+) or Ryzen equivalent (5000 series +), not more, not even for future proofing, though I understand if you want to get i5-level (that qualifies as a lot of overkill IMHO). But the internet connection is probably the most important and has nothing to do with the computer's specs (barring the advantage of a hardwired connection and not over wifi).