Resizing content on a web page

Hi, my name is Francesco Mammetti and I'm a ux designer who works for the
Italian public administration, I had two questions to ask you and I thank
you in advance if you answer me 1 I read that in WCAG the size to guarantee
usability and accessibility in enlargement is 200%, (although I read that
many recommend 400%) I wanted to know if I can still take this value into
consideration? 2 Is there also a scaling value to decrease? Thanks again.
Francesco