Powertardatsch Armstrong is a smaller, stronger, faster, better Pryor. Amd Arguello won't be landing anything close to what he was able to land on Pryor. I think he could shoot at Pep and keep him extremely cautious, and it'd be a close decision. But Armstrong would smother him like whipped cream on a BBW fetish gimp.
He loses badly to Pep most of the time IMO. He is a conventional boxer-puncher with average speed and Pep just made those guys look like fools. Then again, almost everyone loses badly to prime Pep so that's no great shame, at least Alexis has a genuine puncher's chance with his 2-fisted KO power. I think he has a better shot against Armstrong, but still would be the underdog, especially with Armstrong's great chin taking away Arguello's chances of winning by stoppage.