My friends and I have been playing DnD 5e for a few years now, but now I've decided to start GMing PathFinder 2e. We've played through most of the Beginner Box, and now I want to continue with my own homebrew content. As part of my world, I want to introduce a fighter "subclass" (probably the wrong terminology for PathFinder). What I want is a tribe of warriors who fight without armor (starting at level 2 or 3), and to compensate for the lower AC they get magical tattoos which increase their AC. It will also be possible (when you advance in levels) to choose to add other tattoos with other magical effects).
So my question is: Is this what archetypes are for? Because I don't think "subclasses" are a thing in PathFinder? Or how would I go about this?