Any character that uses color, bump, and spec maps (typically Poser 9 characters and up), or color, normal, and roughness maps (for newer textures that are created with software that makes PBR metal-rough) textures will probably not need EZ skin at all, to be honest. They can be updated using similar setup to the P13 SSS shaders updated with Poser 13. The older textures that only have a color map would benefit from a SSS plugin that would achieve bump and shine through nodes vs textures.

Older 3Delight shaders need updating to look their best in iRay, same is true of older FireFly shaders needing updating to SuperFly.