You are being advised poorly by the previous posters.
If you are running solvers and poker software, you don't need a GPU (doesn't hurt either, though) and you do need that ample amount of RAM.
The i9 13900 doesn't overheat. It will ramp up to its max temp, if challenged by your simulations, but it will remain in safe range. The better the cooling solution, the better the performance. Those Noctua coolers are pretty good.
That case is good for airflow, make sure you throw in plenty of ventilators of a decent brand to produce a good airflow in your case. Put this beast into the coolest room you have in your house