Iray Worlds-Plus is a standalone product, you do not have to buy extra morphs, plants, trees or anything else.
All the images used to advertise this product were entirely created with "Iray Worlds-Plus" and no extra products or textures were used. That said if you own or buy the original Iray Worlds Skydome and/or Iray SkyDome Super PAK then you will have access to a lot more water sky and ground textures.
In other words, Iray Worlds-Plus is a new World product that is still backward compatible with the two main earlier Iray Worlds products mainly for textures.
Iray Worlds-Plus is not a small product by any means, but it's very easy to use and it's basically a click and set product.
It also includes many pre made scenes (Images show these scenes) however its designed so you can create your own ultra realistic scenes complete with sun positions, color, range and a variety of light emitting Skies, a variety of ground covers, many types of plants, ultra realistic grass plus a large variety of trees and much more.
Please read the Iray Worlds-Plus user guide for an explanation of how to use the product.
Iray Worlds SkyDome and Iray SkyDome Super PAK are only required for use with the 9 IR-Adjusted MATS and are included as a bonus for those who already own those products.