I will start by saying I realize one preseason game is far from definitive, but these are my observations ...
Jarwin - I like the agility he showed and the smooth, almost effortless way the catches the football. Seemed very smooth in and out of his breaks and making cuts and running after the catch. It's easy to see why the Cowboys like him.
Swaim - Did he even play? I didn't notice him.
Rico - I feel Rico is on the bubble, but at least the few times I made a point of watching him block (goal line situation) he looked good. Since I didn't focus on watching him block more than that I can't say how representative that is of his overall blocking ability, but it did at least suggest he has the basic ability.
Schultz - I didn't notice him much. He looked reasonable on his one catch, but that isn't much to go by. He did get blown up blocking on one play at the goal line, but it's hard to know if that was a fluke or not.