Does the ATLS provide any armor for my character, or does it influence my hitbox? So, would a bullet to the chest count as damage against the ATLS or my player character?

For its initial release, the ATLS is invulnerable, but any bullets that hit the player will deal the same damage as they usually would. For example, shooting a player in the arm still applies damage to the arm along with the associated multipliers.We will be following up in a future release to include damage, visual damage effects, and destruction, so the ATLS won't be invulnerable forever.