Spot size affects how the energy travels through the skin.
Larger spot sizes allow the energy to penetrate deeper with less scatter and are used to target coarse, terminal hair.
Smaller spot sizes concentrate energy closer to the surface and are used for finer, more superficial hair or when more precision is needed.
The goal is always to match the spot size to the depth of the follicle being treated.
Removing finer hair is more advanced and not always the priority in early treatments. But when needed, it can be addressed using smaller spot sizes, higher fluence adjusted carefully, or dual wavelength approaches when appropriate.
Terminal hair and vellus hair do not respond the same. Your approach should reflect that.