Depends if you want it matching or not, but they are usually interfaced (stabilised), as are the collars. Enjoy your break :)

It really does depend on the look you are going after. Sometimes a shirt yoke, cuffs and collar are done in contrasting colors to add a fashion sense to the garment. If it's a sweatshirt, use a fabric called ribbing for the cuffs and neckline in the same color as the main shirt. As you will be the designer...anything goes.