Page 6-15 of the Niro EV manual states Snow Mode disables regenerative braking.
Page 6-33 of the Niro EV manual states Snow Mode characteristics "Provides safe driving on the snowy roads".
Outside those two statements, there is nothing that states what other settings, if any, are changed when using Snow Mode.
Sure, it may alter the throttle response or whatever. But the manual doesn't actually say that. So I guess we don't actually know what it does aside from disabling regen. It must do 'something' otherwise it would be the same as Normal mode with regen 0, and clearly it isn't.
In Snow Mode, Climate system control is Normal (so not Eco), and Brake mode is also Normal (so not Sport).
There are references to things that "may not work" as fully as under normal circumstances, but this seems to be largely due to stuff about sensors being covered. This is referenced across pretty much every driving safety assist feature.