>>275324037
Opaque is for when there is no transparent parts so every part of the mesh has some texture to it. Cutout if for when there is a hard edge to the transparency. Transparent is for when there is a partially see-through part.
For example the eyes might just be a flat square of mesh with a circle for the texture so the corners of the texture are transparent. An opaque shader will smear the eye texture to the corners of the mesh and look broken but cutout will be fine. Transparent will also work for the eyes but apparently this is less optimised, I'm not sure. If they had a pair of stockings that was slightly see-through or a wet shirt or something, cutout would make the mesh completely invisible where the transparency of the texture was over 50% and opaque where it was less than 50% but a transparency shader will allow you to partially see through all of it at varying degrees as intended. You could use cutout for everything that doesn't need a gradient for its transparency but if you have multiple materials and can put opaque on them, you should.