Is it better to wear 2 masks or 3 masks (ns or kns) to protect against covid? there is a study from 2021 that suggests 3 masks provide the most protection against covid. however one doctor says 3 masks are dangerous because it's hard to breathe?

There is a point of no return. Wearing a single mask properly, N or KN is adequate but not a 100% guarantee of protection as other ways of exposure like touch etc can cause spread. Take the usual commonsense precautions and be fully vaccinated. Good luck

Three masks may be a bit of overkill. Are you fully vaccinated with a booster? If so, your chances of severe illness are minimized.