Character mesh low poly in object mode and high poly in sculpt

I used InstantMeshes to clean the high poly character 3D scan object, which had to much vertices to be practical. Now I want to adjust the muscle structure with sculpt mode, and I noticed that the

rendering - heightmap from textures and hight poly mesh to apply

mesh - How do I only select vertices which are visible from my

Mesh Replacement - Blender Stack Exchange

Character mesh low poly in object mode and high poly in sculpt

Mesh Replacement - Blender Stack Exchange

High poly mesh too high - Blender Stack Exchange

mesh - How do I only select vertices which are visible from my

mesh - Modeling stylised fur - Blender Stack Exchange

rendering - heightmap from textures and hight poly mesh to apply

mesh - Modeling stylised fur - Blender Stack Exchange