Who wins? I got Jacobs on points or late stoppage, but can also see him getting sparked out himself if caught with something big. Other than that, he should win comfortably.
I'd also favour Jacobs, I think his boxing skill is quite a bit better than Lemieux. That said, His chin isn't bomb proof steel like some of the other top MW's right now, so you'd have to give Lemieux a decent puncher's chance. 60-40 kind of match.
I think Jacobs obliterates him. Neither are anything special, but Lemiuex is just a short, limited slugger with an big equaliser. Jacobs should pick him apart.
I can't see the fight being any different than GGG and Saunders vs Lemieux. He's getting knocked out or outboxed. He always has a puncher's chance, but that's it.