It still won't matter if he can't read what is unfolding in front of him.
Too many times last year he was like a dog chasing hubcaps.
This is true although we don't know how much of that was a lack of confidence in his lateral agility. He was clearly much more explosive in a straight line so that could've resulted in him taking more risks guessing where the ball was going instead of waiting to read the play out.
At any rate, I'm confident that his mental processing will improve if for no other reason than the presence of Lee. Myles Jack looked completely lost as a rookie and then was a Pro Bowl caliber player last year, if Smith truly is anywhere near 100% physically I expect a similar type of jump.
The good thing is that Vander Esch is actually excellent at reading plays and slithering through traffic/past blocks, so even if Smith doesn't improve much in that regard, we'll have another LB aside from Lee with that ability to diagnose.