Use Cubic control points. +

Import the image.

Scale the image.

Zoom in.

Put the image at the baseline.

Move the guides.

Convert the image to black and white.

Adjust cutoff threshold, the amount of details and the path simplification. The default settings will generate smooth curves with few control points, if you set path simplification to a low value (0.100) and the amount of details to a higher value (2.000) will rough edges be preserved.

Generate vector graphics from your image.