With 1GB of data you only have 1GB of LTE to use per month before you are dropped down to a slower speed. The Unlimited LTE plan costs $80 per line now(used to be $70 I think). So while you have unlimited data, you only get 1GB of LTE speeds. Unless you meant to say that you pay extra for your line to get the unlimited LTE like I do.
The 4 lines have 1GB LTE. My own line has truly unlimited LTE on the phone + 5GB tethering. It's a family plan.
I just checked my account. To add unlimited LTE data on the phone + 5GB tether, it would cost $30 a month.