My understanding is that out of the 2, Fultz can be very dynamic as a 2. He is a PG, but part of his enormous versatility is that he can play off the ball amazingly. It would be interesting to see who creates more offense out of IT or Fultz.
Its like he is a spot up slashing sg, who also happens to be a better point guard.
And for the forwards, I could see Tatum being good at PF due to his frame being slightly more melo/pierce ish (and he is a good rebounder) whereas Jackson has more of the Wiggins/Childress build. Kind of skinny. Athleticism of both make them capable in todays nba however.