Any recommended "realistic" looking nature assets?

Regarding the materials and textures.
I have no capability of making these things. My only option is to buy.
The only asset I have been meaning to buy is this:
https://www.unrealengine.com/marketp…cape-ecosystem
(only problem is it only covers the mountain and humid climate regions)

It seems good enough but I cant really judge.
Also your comments on performance are absolutely right on I will be paying attention.
How do you feel about rocks, cliffs and meshes? Are the no assets that lend themselves well to the Speed Tree assets for a “realistic” look?

Thanks.