Plot hole: Peyton had his face burned in the explosion. In fact, he basically lost his lips, so he should not be able to talk very easily. While he could probably learn to speak normally again through other movements with his mouth and tongue, he does so too quickly to make logical sense. And his uncanny ability to almost perfectly mimic his enemies could probably be learned over time, but again is too quick to make sense.
Plot hole: Whatever happened to the one legged henchman? He was one of the villain's lead goons in the first half of the film, but he simply disappears after the scene in Chinatown. The previous correction that "Peyton didn't have time to track him down" is complete nonsense. He literally vanishes from the film. (Due to a deleted scene, but that's no excuse either way.) There's absolutely no reason he still wouldn't be in Durant's gang and in the remainder of the film.
Suggested correction: You may not agree with the filmmaker's choice, but that doesn't make it a plot hole. It's an unresolved character thread, nothing more.
It's not the filmmakers' choice, though. He was meant to be in more of the movie, but his death scene got cut by the studio to shorten the runtime. So yes, it is a plot-hole, given he was one of the main goons and simply vanishes.
This still isn't a plot hole. In the reality of the film, that character does not partake in any of the gang's activities after the last time he's seen. His presence is not integral to the plot and the story still works without his arc being resolved, so this isn't a plot hole by definition. A plot hole is a gap in the film's logic that cannot be explained, and a side character not having their story resolved on screen does not fall under that definition.
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