>>297575263
Use tesselation rather than subdividing the mesh yourself. unity standard shader doesn't use tesselation, but you can pretty easily add it to a surface shader, or use amplify shader graph https://docs.unity3d.com/Manual/SL-SurfaceShaderTessellation.html

excellent guide on how it works (the rest of the guides are great on understanding how unity rendering works in general, including parallax mapping) https://catlikecoding.com/unity/tutorials/advanced-rendering/surface-displacement/