Your displacement 3D model is blurry after manual unwrapping mainly because UV islands aren’t scaled or aligned to match the displacement map’s resolution.
Displacement maps rely on UVs to transfer detail—if UVs are too small, stretched, or waste texture space, the map’s fine details can’t apply accurately. A high-res map won’t help if UVs only use a tiny part of the texture sheet.
Fix this by resizing UV islands to use more texture space (without overlapping) and ensuring the map’s resolution matches each island’s texture area.