Hi Fantam_Mayfly,
Happy Holidays to you too!
I’m not sure what the DaltR would stand for - but they are being used as diffuse textures - just the RGB no A so it’s pretty safe to ignore.
They will just be using Diffuse for the example - normally you would add other textures like normals as well - the example landscape is mostly hidden by foliage and rocks like you say…
Regarding which to use - I believe the grass tool is faster for setup but both should run at around the same speed in game.