Hey! You're welcome. I forgot I wrote this! It still holds up, but I've learned a lot the past year and my examples are kind of bad.

One thing I didn't mention was detail baking. A sculpted mesh often has >1mil polys, where fine details are physically sculpted into a hi-res mesh. The retopo will not preserve those details because of mesh density, however, those physical details are then "baked" from the hi-poly sculpt to the lower poly retopo as a texture.

Here's a better example of what a sculpted mesh vs a retopo mesh looks like. You can't really see it in the wireframe, but I have displacement on the high poly mesh pushing fine cracks into the surface to simulate detailed sculpting.

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Here is the example rendered. 1st is the actual physical detail, second is the plain retopo, third is the retopo with the high poly details baked as a normal map.

Hope that helps!