Salt doesn't pass through RO membranes and these appear to have the same pore size. However, they all foul and you perform maintenance like backwashing and chemical cleaning as the flow rate goes down.

Here is an overview: https://www.suezwaterhandbook.com/water-and-generalities/fun...

In terms of efficiency, it is cost dependent. Making drinking water is not cost prohibitive at this time but for large scale agriculture it would typically be considered too expensive to irrigate with RO desalinated water. This technology appears to lower the energy requirements but more research and scaling it up is needed.