Computational-Fluid-Dynamics simulations are RAM-limited, iirc.
I'm presuming many AI models are, too, since some of them require stupendous amounts of RAM, which no non-server machine would have.
"diminishing returns" is what Intel's "beloved" Celeron garbage was pushing.
When I ran Memtest86+ ( or the other version, don't remember ), & saw how insanely slow RAM was, compared with L2 or L3 cache, & then discovered how incredible the machine-upgrade going from SATA to NVMe was..
Get the fastest NVMe & RAM you can: it puts your CPU where it should have been, all along, and that difference between a "normal" build vs an effective build is the misframing the whole industry has been establishing, for decades.