Unfortunately, I can not tell you with any certainty the prevalence of breeders that do not use good practices or have the pups' best interest in mind. As in any endeavor, there are those who will take reasonable care and go the extra mile and those who may not understand the responsibilities of being a breeder.
The best any prospective owner can do, be it for a Coton or any breed, is to ask questions and engage in a respectful dialogue with a prospective breeder. A good breeder will welcome informed, respectful questions as it shows you have an interest in your would-be pup and want to ensure he or she gets the best start on life as possible and that you aren't just looking for a quick transaction, but that you're taking a living creature who will be with you up to two decades in the case of a Coton.
Good breeders will be open about how the pups and the breeding pair(s) are cared for and will be transparent as reasonably possible. They may, and likely will, ask you questions because a good breeder also wants to place the would-be pups with good prospective owners.
There are never any guarantees, but by engaging in an open and constructive conversation, both you and the breeder can learn about each other and make the best decision for both you and the potential pup. In the end, that's what counts.