For very delicate underwear, the "air fluff" setting would likely be the best option. The "air fluff" setting is designed to use only room temperature air to gently tumble the items in the dryer without any heat. This setting is ideal for delicate fabrics and items that cannot withstand high temperatures or agitation.
Using the "air fluff" setting for delicate underwear will help prevent any damage to the fabric, elastic, or any delicate embellishments. It will also reduce the risk of shrinkage and help extend the lifespan of your delicate underwear.
Before using the "air fluff" setting, always make sure to check the care label on your underwear to ensure it's safe to be dried in the dryer and follow any specific instructions provided by the manufacturer. If the care label suggests air-drying, it's best to follow those guidelines to preserve the quality of your delicate underwear.