Laundry beads are mainly concentrated perfumes with additives to help the perfume disperse in your washing. Any kind of additive can build up in your clothes and it’s that build-up that can make towels go a bit crusty and unpleasant. The ‘best’ way to wash towels is just with a detergent - fabric conditioners especially can have oils and fats in them that make your clothes feel nice and smooth but can stop fabrics being absorbent, which is why you shouldn’t use fabric conditioner if you’re washing towels, tea towels, anything made of microfibre or sportswear. These are all supposed to absorb fluids and the conditioner, although it makes them smell good, can make them less effective at doing that.