The 19 YOs make it pretty tough. You're pretty much out of luck as far as the u21 is concerned.
The first player is out entirely I would say. Not good enough height to train as a big man at that level, and not good enough starting stats to train as a SF or guard.
The 2nd player is a bit more enticing. Good height and potential and servicable big man starting stats. The ATR passing is a bummer though... Based on the low secondary stats that he has, if you want a NT player out of him, you should focus on REB, IS, ID and build a monster. He will also be a salary issue down the road if you take that path. But again, the 19 YO part makes him a bit of a long shot for a NT.
Even if you don't make NT, the second guy will be a great big man for you.