Agreed, while I like Matheson I could go on and on about how he's not a great fit on PP1.
His strengths on the PP are his skating and his shot (except his selection is poor and often shoots when there's a better play available). Except his skating isn't all that valuable given they just use the Suzuki drop pass for entries anyways. Meanwhile his playmaking is just not that good, you won't see him thread a smart pass through a seam, and he doesn't use Slaf's side of the ice the way he should be. I don't like the way he defends on the PP either, he bobbles the puck a lot at the line, and I find he is always WAY too casual when defending counterattacks, probably part of the reason we've allowed so many SHG this season.
Arber's strength would definitely come from his shot, which is better and more powerful than Matheson's. His shot has so much power that he'll create a lot of havoc putting pucks to the net and generating rebounds. His skating and entries I think are actually pretty good too, while not Matheson level I'm seeing him do it a lot more recently and do it pretty well. It pretty much comes down to how well he can distribute the puck, and honestly I don't think he's any worse than Matheson is.
It's worth a shot trying him for sure, but I don't think it's gonna happen this season.