First things first, box scores don't mean much at all and as appealing as 19-19 and 50 points is, focus on the more important things like potential and age. Also the heights for these guys would help me out in giving my opinion as well.
Personal belief on my part is that you should never turn down a 5/5 prospect, however depending on his height, an A- could be unfortunate for a big because he secondaries might suck.
The two SFs are nice and 5/4 A+ player is always good, but I think I value the 5/5 18 year old more. Had the 5/4 A+ player been 18, I would be more prone to say put him first, but at 19, I think the 5/5 18 year old is much better. Even if the big isn't as convenient for training, he will ultimately be the best prospect and I'm sure you could work it out with your other trainees. a 5/5 big could easily become a cornerstone for your team. I would go:
1. 18 year old Center
2. 5/4 A+ SF
3. 5/3 A+ SF
I also think chances are, you will get two of these three guys but no promises.
Murray/Harris/MPJ/Grant/Jokic - 2020 NBA Champs