Basically JK provides a terrific outside run threat with a great jump cut. He won't be running up the middle much with his smaller stature but will provide a great compliment to Ingram's bruising I'll knock you down and out of my way style.
JK was also able to capitalise on Fields (limited) running abilty threat which is obviously something he will be able to benefit and exploit more given he'll have Lamar drawing a lot more attention from defenders.
We'll need to develop his receiving skills more if Roman wants to engineer ways to create opportunities for him in open space. JKs speed and agility are his best assets so giving him as many chances working against defenders one on one in space should be a great weapon for our offense.
Lamar will also benefit from JKs addition. With JK giving defenders a lot to worry about on the edges that will only create more lanes for Lamar to run through on the inside.
Also notes that JK needs to work on his pass protection so he can be trusted on the field in any given situation.
The article obviously went in to greater details with tape and examples and lots of X and Os talk but that's the gist of it.