“Hard” race realism may be described as the belief that average differences between the races exist and are fundamentally immutable. For example, Africans have a lower average IQ and this will not change. This belief logically requires some form of Platonism and has to be force-fit (e.g. by Nazis and the Alt-White) into the Darwinist paradigm. It is explained at excessive length by Intelligent Dasein here.
“Soft” race realism may be described as the belief that average differences between the races exist but, because these differences initially arose from differential selection, these differences could be ameliorated or even reversed by future differential selection. For example, Africans have a lower average IQ but if eugenic conditions prevailed for long enough they could have an average IQ equal to or greater than Europeans in the future. This is, AFAICT, the default opinion of secular HBDers and the Protestant wing of the Alt-West.
I’ll define “semi-hard” race realism as the belief that average differences between the races exist initially arose from differential selection and could therefore change, but because the essence of race is pleiotropic selection and almost all of the traits we care about are also pleiotropic, it is impossible for a race to undergo such selection and remain essentially the same race. For example, Africans could undergo intense eugenic differential selection such that they had higher IQs than Europeans, but in the process they also would become a fundamentally different race. They would look fundamentally different, have completely different cultures incompatible with the old ones, develop new and different languages mutually indecipherable to the old ones, and so on. While it’s clearly true that high-IQ populations need not converge to the same appearance (etc.)–e.g. Asians and Europeans look different–it’s not obviously true that high-IQ populations can have the appearance (etc.) of today’s low-IQ populations–e.g. Africans and Australoids look the same via convergent evolution specifically to a 65-IQ niche.
Also, “semi-hard” calls to mind an unenthusiastic erection, which is amusing.