Written by Matt Guilhem, KCRW
The costume designer Deborah Scott has been working on [the film] since 2018. Scott and her team created all of the live action costumes worn by the humans and the Na’vi. She had to create each and every one of them because [the actors] had to do fittings. They all had to wear the actual costumes to see how they moved even though they never appeared on screen. So every costume, including the props, the masks, and the helmets, took about a year to make.
After they had fittings it was all given to post-production to go digital. But yes, even though it was all CGI, the actual costumes were physically made.