Those pinched joint deforms I see in your example are a result of your rig, not the density of the polys. But to further smooth deforms in Layout, you may also want to apply subD (Tab key in Modeler). In Layout, Object Properties (P key), set Display and Render subPatch levels to suit, and set SubDvision Order to at least ‘After Bones.’ This way, the subD will apply after the bone deforms, thus smoothing.
To reduce polys, there is also SubD Recovery http://www.mariussilaghi.com/products/subd-recovery that should revert existing subD on Daz models, while maintaining quads and correct poly flow. Only works with quad models. Since we usually dont know if a given Daz model was subD’d at some point, it may or may not work on a given model. I assume this works similarly to Zbrush Subdivision Reconstruction (Geometry menu), which has worked for me for at least one level of subD reduction on any Daz model I have tried. But in ZB, I have not been able to figure out how to keep surfaces/materials/UVs intact when exported.