Before that try an AVI test instead of MP4.
As you may have issues in warranty of.your Prebuilt  PC the new one which you have purchased.
All the best... And do get a good SSD for video outputs.

I'm finishing a movie just now, to be posted soon. It's rendered in MP4 but in 4K. So I'm serious about the quality. For my next movie, I intend to render in AVI uncompressed. I just learned of its benefits too late.

As far as rendering to my SSD, I tried that with my new computer. It takes longer than if I render to my HDD. Almost wice as long.

That's why this new Alienware Aurora r14 from Dell is going back! I'm going to build my new computer myself, like I used top. Dell gives you some choice of components, but not enough. As for the CPU. for example, they don't really give you the choice. I wanted a high-end Ryzen threadripper like in my old computer. I got a lowly Ryzen 9 5950X. Dell gives you what they think is good for you and what they can get away with. I'm very disappointed with my new computer. Like I said, it takes FOUR times as long to render as my old  computer Now if it took TWICE as long that would already be prohibitive, but FOUR times!? Are you kidding? This computer is going back.


My latest movie THE GOLDEN MAN, and a few others: https://www.youtube.com/channel/UCIl1EqVCKitZzLqaNnLK0BA

That is a peculiar result and in contrast with my own experiences with the same type of PC.  Also, the CPU shouldn't really have that much effect on rendering times. I'm thinking there may be something wrong with the build.

I usually build my own PCs as well, but last year it was impossible to get an RTX 3090, so I went with Dell.

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Hmm wish I could get your PC, but we don't have that option in my country. ☺️

As Animagic states, your New PC seems to be very capable and slower result on SSD seems to be contrasting result from other members that tested a simple scene with me last month in my benchmarking thread.
We all had fastest render on SSD with both MP4 and AVI.

Still your scene must be pretty heavy.
All the best from me.

All I can say is that maybe there's something's strange with my computer. Dell support says usually my problem is caused by the CPU or maybe the RAM. But I think it might also be the motherboard. It's not the top-ranked  motherboard, It's a B550. 
 
That's why I'm returning it. For the money I paid (UDS 5600), I had the right to expect a computer that delivered more


My latest movie THE GOLDEN MAN, and a few others: https://www.youtube.com/channel/UCIl1EqVCKitZzLqaNnLK0BA