This is an exercise. I don't use much software. It's just that there is a back and forth when dealing with the edges. I found that if I did the smoothing too early when doing it initially. However, manual topological hard edges are always prone to the problem of not being straight or round. The best thing to do is to do it all over again. I don't do UDIM textures for this model. Just put it together as much as possible and export the 4K texture.