The title pretty much sums up what I'm trying to do, I'm trying to make it so upon choosing a certain subrace for another race will make them bound permenantly to a type of equipment like armor, similar to how Warforged work in that matter. Should I just use a modifier to override the AC or is there a better way to do that?

You could do it as an override or a bonus. What exactly are you looking for?

Something along the lines of it showing as light armor on the character sheet, since its a permanent equip of the armor.

Then set the Unarmored AC and explain it in txt. Don’t forget to include a “you are wearing armor so can’t actually equip armor” clause too.

But Warforged don’t work that way. They just get a bonus when they are wearing armor.

It sounds like you want more Tortle than Warforged.

Ah, then I thought about it wrong, still I thank you very much for your help.