depends if you need the edge to look soft or hard. https://polycount.com/discussion/107196/youre-making-me-hard-making-sense-of-hard-edges-uvs-normal-maps-and-vertex-counts#latest
The edges where UV seams are could be split/hard /sharp since a game engine would split such edges anyway and edge vertex count will be doubled at such edges. Any other edges should be smooth/soft and making them hard where no UV seems are just makes extra redundant vertexes to calculate and troubles for normal map baking.…