A chicken being a sex link does not mean anything about egg laying ability. Chickens inherit egg laying ability from their parents. If the parents are good egg layers, the offspring will also lay well. You can use good or bad egg layers to make sex links.
Some hatcheries use specific breeds to make sex links. There are a lot of different possible mixes, but some common breeds used to make red sex links are Rhode Island Red or New Hampshire roosters over Rhode Island White, Delaware, Silver Laced Wyandotte, or White Rock hens. Rhode Island Red rooster over a Barred rock hen is a very common way to make a black sex link. These chickens normally lay well because the parents lay well. But if you take a Barred Rock rooster and put him over a Rhode Island Red hen from the same flocks, these will not produce sex links but the offspring will lay equally well.
Some hatcheries don't cross specific breeds to make their sex links but instead use commercial egg laying chickens. These have been developed through selective breeding over many generations to produce a chicken that will lay a lot of large eggs, perfect for the commercial industry. They have a small body size so they don't use a lot of the feed they eat to maintain their body. Instead you get a real good feed to egg production ratio. When people get these commercial sex link chickens, they get blown away by the egg production. But these can be more prone to egg laying related injuries. Some advantages, some disadvantages.
So don't buy the myth that the chickens are good egg layers because they are sex links. It is not true. They are good layers because their parents were good egg layers.
Another myth pretty prevalent on this forum is that you can sex any chick by the wing feathers at hatch. Study the last section of Tadkerson's post. You'll get a scientific discussion on what it takes to be able to feather sex. And if you really look at it, you can see why it won't work with just any chick.