Ryzen 5 5600X vs Ryzen 7 5800X: How important are the two extra cores in Trainz?

So I'm playing with the idea of a new PC build. Well, I have been for a while, but the whole Windows 11 fiasco has kinda rekindled that interest.

The hardest decision I've had to make was the CPU. I'm currently looking for an AMD Ryzen CPU, and I was certain I wanted a Ryzen 7 5800X. But then, I had brought to my attention the Ryzen 5 5600X.
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The R7 5800X (MSRP US$449) is an 8 core, 16 thread CPU. It does not include a cooler in the box, so add the price of a good cooler.

The R5 5600X (MSRP US$299) is a 6 core, 12 thread CPU. It's currently $149 less than the R7 at MSRP and includes the AMD Wraith Stealth cooler in the box, which I understand is pretty good for an in-box cooler, as long as I don't intend on doing any overclocking (and I don't). The savings from the CPU and not having to buy a separate cooler would basically buy the motherboard.

For a GPU, I would reuse my existing overclocked GTX 1070 8GB, but explore RTX 3070's or 3080's when prices get closer to normal.

All benchmarks and side-by-side comparisons that I can find show that gaming performance between the two CPU's is 100% identical. Rendering is another story but I don't really plan on doing any of that. But there's one game that I can't find a comparison for; this little game called Trainz Railroad Simulator 2019. Maybe you've heard of it?

Now I'm not entirely sure how different Trainz is from, say, Red Dead Redemption 2, or Shadow of the Tomb Raider, but I would imagine Trainz would perform just as well on a 6-core CPU than an 8-core, right? I mean, multiple reviewers are calling the 5600X "the best CPU for gaming".

This raises the question that I'm sure has been asked many times here - I'm pretty sure I've even asked it here myself a time or two - would those two extra cores of the R7 have any benefit in Trainz over the R5?

And a bonus question: Is the included cooler with the R5 worth my time, or should I still investigate a different cooler?