I see, thanks for the extra information, CreativeRaul.
If the polygon number is too high, it might slows down everything of course, you’re correct. If that is the reason, perhaps you have the Activity Monitor open to see if there is some heavy lifting done, which doesn’t show the CPU activity, but perhaps you find the GPU and memory activity working hard to get something visible.
Rule of thumb, polygons smaller than a pixel are a waste of recourse. Sounds maybe weird, but with SubDivision Surface and Sub-PolygonDispalcement such situation are easily established, with no advantage.
A good mix between displacement (for larger and medium details) and bump mapping (for finer details) is certainly worth testing.
If you go to Editor View>Options>Configure All>View and in that tab, enable Back Face Culling, you might get some speed back.
Agan, my best wishes.
Sassi