Materials render different in MAterial Editor than Viewport

I am fairly new to Unreal, and starting to work on materials, rendering and creating levels. I seem to always come across an issue where I get something looking good in the material editor, and then when I place in the level and look in Viewport, and renders completely different and I cannot figure out why.

I usually end up changing values on the material, often making areas of material partial metallic which would be non-metallic just to get a proper look in the viewport. I figure this isnot correct and something else needs to change.

I am using 1 directional light set at default 10lux which seems to light my landscape material correctly. I have skylight, static lighting disabled in project preferences, however my ligts are se to static (changing them to movable does not change any rendering effects in viewport).

I have attached images of material editor, viewport and the Base Color, Metallic, Roughness and Normals.
I also attached images of the material, which looks complicated, but just simply allows me to make a lot of custom adjustments in converting the original specular workflow textures to PBR.
And instead of using Multiply and Power to adjust Brightness and Contrast of texture channels, I created a custom function which is fewer instructions, uses only addition and subtraction and gives me greater controls over image levels than just brightness and contrast (power).

Curious to know if anyone else runs into this situation and/or knows of settings somewhere that I am not utilizing or using properly?