I don't know for certain but I am betting cherry shrimp would survive just fine in mildly brackish, they are pretty tough little critters. BUT if you did adapt them to even mildly brackish conditions when it came time to sell off any offspring, you would have to warn buyers of the exact water parameters you have conditioned yours too, other wise they would probably just die if put straight back into full fresh water.
Rhino shrimp are quite similar to Darwin Red Nosed Shrimp and previously had been misidentified as the same species. Darwin Red Nosed shrimp can be bred in fresh water, so you may get away with breeding rhino shrimp if you have particularly hard water. The larval stages of the young is the hard part about raising these shrimp though.