Thanks, E, for the question.
The R is placed on the cloner to position the image information in the way it is needed. So one can adjust it interactively. Sometimes I use a Plane object for that, while the Plane object has the size of my intended size of the texture. I find that more intuitive and comfortable. The Plane can be invisible (but active) to provide this data.
The X in the Selection is used to shut the Material off for this object. Since there is no selection called X. I used this since ever. Delete the X, and the Image/Material is visible on the object. If it is on the Displacer, one can’t see it as an image. The X doesn’t stop the flow to the Displacer.
(To have that Material Tag (formerly know as Texture Tag) on the object allows me to know its use even after a long time.)
With that being set up, I can use this Material Tag in the Displacer Deformer and select which channel I like to use.
Is there an one and only or THE right way to do it? No. I like to suggest exploring all options and stick with what makes the most sense to you. The more routine you get, and things that become a standard, the more your energy can go into creating, rather than organizing.
The downside is, you get less “happy accidents”.
My best wishes.
