1st: Say if Person One is inside of a visible Barrier and Person 2 (Kamui User) Is outside of it would he be able to Kamui the person inside or would he Kamui the Barrier instead?
The barrier is hollow, it's not some solid encased object that the person is residing in. It's the same as if being in a building and seeing through a window; as long as the Kamui user is focused on a certain point, the hole will open up there and take in what the user wants it to.
It seemingly works similarly to Amaterasu. Sasuke was encased in ice (and sometimes within Susano'o) and yet could still Amaterasu either further within the ice, or completely outside of the Susano'o, because that's where he was seeing.
So theoretically if Sasuke or Kakashi wore glasses, Amaterasu and Kamui would still work.