CFAN mentioned it in another thread, but moving Pritchard & a future first round pick to Houston for #20 would be a pretty good move by my standard. As much as I enjoy putting together big trade packages, I don't see any happening with this group.
So, that leaves us with picks 20 and 35. I think we could nab two solid players at these spots.
20: Trayce Jackson-Davis. It might seem like a reach to pick him here, but I see no chance he falls to #35, and I think he can be a legit starter in the future. High-level athlete who uses that to real advantage both defensively and on the rebounds. He has a great second jump on rebounds, sort of like Timelord. He developed into a really good high-post playmaker, which is something we need to offset Horford's ageing. I could see him becoming a super damaging short roll player too. Good screener, rolls with speed and has the ability to finish at the rim, has a 7'1" wingspan, and he is smart on defence - barely fouls. I think he could be a bit like Draymond if he keeps developing, except he's bigger and worse at shooting 3s.
35: Keyontae Johnson. I should preface this by stating that I would only pick him if our medical staff are super comfortable with his heart condition. He is a physically imposing wing at 6'6" and 240lbs, with a 7' wingspan. He has a significant amount of offensive versatility, and at worst would be able to immediately provide what Grant does on offence. He's a good perimeter shooter, can draw fouls at a good level, and can bully smaller wings with ease. He is a very strong rebounder too, and loves to play a physical brand of ball.
We don't have too much to play with in free agency. I think Davison is still a year away, so I would look at Cory Joseph as a back-up PG. I trust Jackson-Davis to be able to contribute immediately, so much so that I would be comfortable not adding a big. With the team as below, I think running it back is fine. The coaching additions will help a lot. Give Brown his supermax, and if in 2 years the team has done nothing then ship him off.
Smart / Joseph
White / Brogdon
Brown / Hauser / Johnson
Tatum / Horford / Gallinari
Williams 3 / Jackson-Davis / Gallinari