Fenech might have some success and do well but Arguello would just be too much. Fenech was great at closing the distance, but he would be met with a lot of short hard shots from Alexis. He could generate a lot of power with short punches that don’t travel much distance, like the two punches he dropped Olivares with. He would probably also land that right uppercut to the body a lot.
One potential advantage Fenech could have here is that Arguello may not have been as seasoned or physically strong down at 126 as he would be at the higher weights. Still, trying to outslug Arguello at close quarters is going to be a tall order at any weight, for the reasons Erratic said.