Generally speaking, the crotch width mainly depends on the design and use of underwear. For example, some tight underwear may need a narrow crotch to better show the body curve, while some loose underwear may allow a wider crotch to provide greater comfort and support.
Therefore, the best advice is to find underwear suitable for your body and comfort, check the product description or consult the merchant when buying, and understand the specific crotch width information.