I don't think that Haney is fast though, and I think he hasn't face a fighter that is very quick. He was almost beaten by an old Loma and there are those who think that Loma was robbed during that fight because he was wobbled and Loma try to rally late in the fight.
But I do agree that this could be a chess match, Prograis trying to hit that one punch, and then Loma trying his best to avoid it. So who ever adapts and had a good ring IQ might win this fight.
I actually think that he is fast and we also know that guys who are more muscular and have a lot of muscles are generally not that fast. So I think Haney is going to be alright.
One thing that might be a problem is him not being very confident. As you said, he almost lost against Loma. That is definitely going to give his opponent more confidence. Prograis is definitely going to be harder to beat. Each of them has to predict what the other is going to do. That's the way both of them will be able to avoid the opponent effectively.
I don't know if Haney will feel inferior against Prograis. Loma is a different fighter than Prograis; in fact, Loma was included in the top pound-for-pound boxers in the world, so he is more popular compared to Prograis, whose name is relatively new despite being the current champion. So, I guess Haney still has the upper hand here; he is the more popular boxer, and I don't think he will face any problems with his performance in a higher weight class.
It's because 140 lbs is not that well known, but if haven't heard though, there are two champions that have unified that division recently. Crawford did it first and then Josh Taylor who beat everyone, including Regis Prograis to get all the 4 belts. But it was short lived though, because after being undisputed, he lost all the belt, have a close fight with Jack Catterall, who the majority thinks he lost, didn't give him the rematch. And then he fight Teo Lopez and lost badly.
And eventually Regis got another belt become a champion. So he is not like a push over fight for Haney. It's going to be very difficult for him, although Haney could have all the tools as he is one of the best defensive fighters we have today. And so he might avoid that power of Regis and score points and win in the judges score card. It could be boring for some fans though if Haney will just play defensive throughout the fight. But that is his style and so Regis should be more aggressive and be a volume puncher here and not feel in love with his so called power.