Ok, got some time.
I think it's going to be Brook who is going to be surprised. See E can box and work Brooks body even in rounds he might lose (which will slow him down). The damage will come from our end. Everyone knows his straight and UC combo. He gave it away vs. Gennady. If you can see a punch coming you can take it. Choreograph the ring work to mirror what every punch he throws. Honestly, I'm looking more at his fights with Hatton and Porter. I think those show his tells.
Brook took an onslaught from a much bigger Golovkin and finished on his feet, his body broke down but his chin held up pretty well considering the punishment he took. Porters not exactly a pillow puncher either.
I think you might be surprised at how it goes on the inside, not that Spence doesn't have an advantage there, more to do with Brook tying him up. Brook's strong for the weight and has good clinch control, I imagine he'll fall into his straight rigtht and clinch straight up, smothering Spence's work and forcing a clean break.
You're right that Spence has some set combinations that he uses a lot, he's not super versatile. With that said, Floyd Mayweather used the same combinations and punches for over a decade. They both rely on timing, and it's difficult to stop shots from a guy who doesn't waste anything and times his explosions. Spence needs to show somthing that he hasn't show before, he needs to show better defense and be more disciplined with his offense, he really can't afford to be taking shots from Brook here, certainly not relying on walking through them.
Brook's very good against southpaws, it suits his punch selection more and he's always been around them in the gym, if I had to highlight a couple of things for you I'd say take a look at the lead left hook. He comes up high when he throws it so there's not much opportunity to counter, but he looks to use that punch to stop his opponent and line them up for an uppercut or right hand. Constant evasive head movement after taking one on the gloves would counteract this. He'll change this up for the left uppercut too, he can lead with either one
He'll also overcommit the right hand, and change to Southpaw on the follow through to back his guy all the way up. He did this multiple times against Frankie Gavin, which is a fight you should definitely watch. In short, don't back up from his right hand, step back and bend at the waist, which Spence does in fairness.
I know that you will know all bout the jab and straight right, those are the obvious weapons.
