Spinning tops are notoriously difficult to print in one piece. No matter how you orient it, one side will look terrible. Cutting it along the "equator" will leave an ugly seam where the parts are glued together, and can easily cause the top to become unbalanced and wobbly.

This is sort of a compromise. There's still a seam, but it's on the underside and barely visible after sanding. If you use a material that doesn't like to be sanded, try printing the top layers in a concentric pattern.

The customizer isn't for changing the shape of the top, but for adjusting tolerances and detail levels. The default values create a nice, snug fit on my Prusa with SteelFill, but your setup may need something different. Prepare for trial-and-error.