Teeth whitening after orthodontic treatment

After completing orthodontic treatment, I now have the device removed and go for a check-up once a year, but orthodontics

After removing the device, tooth discoloration occurs, and it sometimes bothers me. Orthodontics I attend.
They recommend whitening toothpaste at the dentist, but I don't think whitening toothpaste is very effective, so I looked into it and found that it is received at the dental clinic.

There is whitening and self-whitening that can be done at home. I heard that whitening is really bad for teeth? gums?

Will my teeth and gums deteriorate a lot? Or is there something called dental veneers, like whitening and veneers?

Which procedure would be better to undergo? Is there anyone who, like me, is worried or has tried it?