If I were you I wouldn’t simplify too much in RC. You want to keep as much detail as you can until you have baked your maps, then you can move forward with your low poly retopo and your maps. I do my retopo with Blender, but it’s the same principle. Model it using large quads just to get the chunked out edge flow, then subdivide/shrinkwrap for medium detail, and then bake the rest. Ballpark numbers (for shoe), 1 million high poly -> 10k low + normal map virtually the same.