Retopo:
i think there are some misconceptiosn about this…you can “retopo” as in create new topology to allow further deformations or you can “retopo” for a particular flow or for optimization purposes
Auto Retopo in the first context will be something like what remesh does: a retopology on the fly with evenly distributed quads…but this resullt doesnt gurantee neither a specific edgeflow nor an optimized density
optimized density=more polys were more curvature is needed and less where its flat or straight opposed to evenly spaced quads everywhere.
This is what explains the general misunderstanding about topology since a “good topology” will always be a compromise…a personal choice, a pipeline compromise and a technical limitation.
an evenly spaced mesh is less optimum in desnity than an uneven one…a mesh made of only quads is less optimized too…tehrefore if you want evenly spaced and all quads you will end up with much higher res meshes and if you rather have optimized meshes you will end up with, in its more extreme form, a triangulated mesh.You can actually witness this while using Decimation Master which using a curvature based algo is capable of representing a surface why identical detail using a very small fraction of the original mesh density