I think the best-case scenario right now is the #24 pick for the Nets and the #19 pick for the Clippers. The Nets and Cleveland will obviously be #24 and #25 in some order. If the teams finish with identical records, I have no idea which team gets the earlier pick. Nets went 2-2 against the Cavs this season. Is conference record the next tiebreaker? The Nets and Cleveland have the same number of conference wins (Cleveland currently has one more loss).
As for the Clippers, right now, the #21-#23 picks will go to the Clippers, Memphis, and Denver in some order. The teams are essentially tied in the standings. Sacramento and the Lakers are a few games back, but it is not impossible for one or both to pass the Clippers. Note that the Clippers are something like 15-16 in their last 31 games. It really is just their 14-5 start that is keeping the team afloat (and a couple of key victories in the past two months over San Antonio, Phoenix and Denver). If the Clippers go 1-4 to finish the season, it is possible that the Lakers and/or Sacramento could catch them. I'd be happy with the #21 pick. When you think about it, had the Clippers duplicated their recent 15-16 record over the course of the season, they'd have something around the 14-17 pick--not all that better than #21.