What does this mean from a fantasy perspective? Let's start in New Orleans:
Pelicans get an absolutely perfect fit
Mirotic is a rugged stretch-4 who can score from inside and out and can help out on the glass. This is exactly what the Pelicans need this season after the unfortunate loss of DeMarcus Cousins.
Anthony Davis and Cousins showed that they could work together as twin towers, but that was primarily because of the versatility of both players' approach, as they could alternate being inside and out. However, the past few years have demonstrated that Davis is not nearly as effective when paired with a traditional center. Davis works well with big men who can be perimeter threats, as well as handle some of the dirty work inside.
Enter Mirotic, who has been having the season of his life even before the trade. Check his stats per 36 minutes from this season thus far:
24.3 PPG (47.4 FG%, 82.3 FT%), 9.2 RPG, 4.0 3PG, 2.3 APG, 0.9 SPG, 0.8 BPG, 1.8 TO
This is the rare situation in which Mirotic is joining a team with which he could legitimately average exactly those numbers for the rest of the season. The Pelicans have a production and minutes hole that fits Mirotic perfectly, and he can maximize individually while simultaneously helping the Pels make the postseason. Fantasy-wise, this is one of the best fit trades that I've ever seen.
As for the rest of the Pelicans, the big losers here are E'Twaun Moore, Dante Cunningham and Darius Miller. Moore was the de facto third option on the team after the Cousins injury, but now he returns to being a role-playing shooter/scorer but at a lesser volume. Cunningham had been starting, but he is currently hurting and should return to his bench role. Miller had an opening to step up as the stretch-4 in a small-ball lineup, but now he has been made redundant to the better Mirotic.
Jrue Holiday still should be a primary fantasy producer, helping bridge the production gap between Cousins and Mirotic. Moving forward this season, the Pelicans now have three front-line, impact fantasy producers in Davis, Holiday and Mirotic.
Bulls power forwards gain opportunity by subtraction
The Bulls had three startable power forwards to squeeze into only one slot prior to the trade. Rookie Lauri Markkanen is both the present and the future of the position, and with Mirotic gone, he should be able to increase his minutes and role at the rate that matches his development.
The bigger winner here is Bobby Portis (available in 75 percent of leagues), who has flashed with fantasy impact potential over the past calendar year, but that often ends up lacking the opportunity to produce. On the season, these are Portis' per-36 numbers:
21.3 PPG (47.6 FG%, 82.1 FT%), 11.0 RPG, 2.8 APG, 1.6 3PG, 1.0 SPG, 0.5 BPG, 2.1 TO
In Portis' case, he still won't have 36 minutes' worth of opportunity on a game-to-game basis because he'll still be playing behind Markkanen. However, he does project as the sixth man now and could legitimately get 25 to 28 minutes per game on average. With that much time, he makes for a potential fantasy starter moving forward.