Yeah use procedural terrains with displacements BUT you need a beefy PC for that to be honest. Long time to render LOT orf RAM needed.
Actually best to use mixed materials for that displacement trick, assign mixed material so displacement mat is only on cliff walls so you can control it more neatly, and no displacement mats where not needed, thus less RAM needed ;)

Note also, no one says you have to use ONE terrain ;)
a good trick is to use terrains poking through to give variety etc

but displacement should be fine

images like that road do require large size for smoothness, but you cna also help hide roughness with adding trees, edging items like rocks etc next to roads. Some post work can also help painting things in/out, blur etc.

:)

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