IIRC, there's also a 'gotcha' where you may set whatever material displacement you please, but rendered extent is limited by oft-overlooked 'Displacement Bounds' dial in object / figure properties. Releasing that turned my lawn render's 'STILL looks like Astroturf' into 'High as an Elephant's Eye'... Oops... Whatever, I went on to 'displace' a flat base-plate into an awesome volcanic caldera with towering cliffs...

There's a tangential issue that some imports, typically FBX, do not seem to support subdivision levels: Their slider is greyed-out. Reason seems undocumented...