After subsequent viewings of Endgame, I think Steve must have gotten a stat boost, it's the only explanation. When he used the hammer, he hit Thanos with a flying knee in the chest and Thanos felt it. Keep in mind Thanos was just slightly stronger than FatThor at the time. When Thanos caught Stormbreaker and tried to force it into Thor's chest, they both had both hands on the axe and Thanos was very slowly succeeding. That means he's physically stronger than FatThor, but not by fucking much (meaning FitThor must be physically stronger than Thanos BTW). For Cap to hit someone like that and make them feel it, which he did, there is no way the hammer didn't boost him. Especially considering at the opening of the brawl Thanos hit Cap and sent him flying, yet after he got the hammer Cap was on the ground and Thanos straight up punched him in the chest, clearly putting effort into it, and Cap was able to get up. If Thanos was even half as strong as Thor that should have killed Cap. I don't think there's any doubt the hammer boosted him, it's literally the only explanation.
As for Wonder Woman, she's shown she can handle lightning but the hammer is much less concentrated than what Ares had. When Cap called down the bolt on Thanos when he was on the ground it was hitting him all over, his entire body. Diana's bracers can't absorb lightning that's not actually hitting them. She'd get some of it, but not all. And with speed equalized and Cap's superior weapons and combat experience, he should take this fight, 7/10.