Like Chychrun at 4, we already have Rielly and Gardiner, Juolevi would be more of the same on our blueline (LHPMD). However...
The Nylanders would make for a potential fan favorite pair and Tkachuk could inspire the Leafs to aggressive go after Dvorak. Now that would leave the franchise thin on blueline prospects but consider what we're looking for in top tank picks....
A 1C, 1D another top six forward are the biggest needs IMO.
Nylander and Tkachuk fit the bill for that top six player and 2017 top ten picks project top to bottom as centers and blueliners with size. Likely to find someone as good if not better than Chychrun. So if we're at 4, fine with trading down a spot or two.