AT&T customer thinking of switching. I owe on phones and curious about some functionality on TMobile...

Hey,

So I have AT&T family plan and am thinking of switching to TMobile, only need two lines and we are bringing our phones with us. I have two questions.

1. If I still owe on the phones on AT&T, do I need to pay the phones off before switching? I think I may also be stuck on a two year contract (would have less than 1 year left).

2. I have a Samsung Galaxy S6 Edge Plus. My questions is regarding enhanced functionality, such as being able to see my Wife typing a txt message to me, or seeing when she's read it, etc all in realtime using the phone's built in txt message app. I believe this to be part of AT&T's enhanced LTE functionality, but I am not 100% Is that functionality capable on TMobile as well?

I'm always afraid of switching due to the 'I didn't know that was an AT&T only feature' type scenarios.

Thank you.