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After further research, I figured it out.
If you wanted to increase the size of a specific tile by two times, all you need to do is unlock the tile flags and set the new scale matrix like so:
Matrix4x4 newMatrix = Matrix4x4.Scale(new Vector3(2, 2, 2));
Tilemap.SetTileFlags(position, TileFlags.None);
Tilemap.SetTransformMatrix(position, newMatrix);
There is ...
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There is no way I will cover every possible style out there.
I will mention pixel art, because it is probably the one that requires more care, but I'm not going into much detail here. DMGregory has done a better job than I could over other answers already linked in comments: here, here, and here.
I will suggest a general style independence approach. And then ...
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