I'm not familiar with how Daz does their character eye setups, but assuming the eyes are a separate object that is attached to an animation bone, then it's trivial to replace the Daz eye objects with EyeAdvanced prefabs once the character is brought into Unity. Defult settings should give you a pretty good start as far as eye rendering is concerned but you can tweak the material settings from there. EyeAdvanced works all the way up to the latest Unity versions so Unity 2019 should not be a problem.