As for the OP's question: I think you'd see an elite 43 LB who is very good at finding the ball and sifting through traffic. IMO, he'll be really good when asked to go after the QB on a blitz... but I don't think he'll get asked to do that a lot. He almost never misses as a tackler either. He excels at breaking down in the open field and not letting the runner get past him. Very secure tackler.
That's the thing about 43 LB's. It is difficult for them to make that much of an impact on the game. They really aren't asked to go get the QB... they're just told to go find the ball carrier and get him down. Of course, they spend a lot of time in coverage as well, and Jaylon is very, very good at that if he's 100%.
I think he'd be very comparable to Patrick Willis or Luke Keuchley actually. If healthy, he's going to put a hat on the ball carrier early and often, and he's going to get home on the few times he's asked to blitz the QB. I wouldn't expect that type of play immediately from him but if he's 100% by the 2018 season he could be as good as them.
He's probably a better athlete than either of Willis or Keuchley, and his length is better than theirs, but his instincts aren't as honed at this point. That's the case mainly because he played the Will LB spot and then was moved to the Mike position. He wasn't able to really get used to OLB before he had to learn to play inside. IMO, it isn't because of any lack of football IQ or instincts... more that he just doesn't have the time at one position to fully develop his game.
Of course, the real question is: Will he get back to what he was? Nobody knows at this point, but as they say in Texas: "We're about to find out."