All of the AEM-7 electric locos (RIP...) were 125mph capable, as were the Amfleet passenger cars, so NEC regional & corridor services could run at 125mph if operated with all-Amfleet consists.
My recollection (maybe wrong?) is that in the late 90's when I used the corridor services occasionally, the Metroliners ran at 125 mph with an AEM-7 and Amfleet coaches but the regular corridor trains didn't go as fast. They were of course AEM-7 hauled and I suspect they were also all Amfleet though maybe they had "heritage" baggage cars. And the overnight one (Twighlight Shoreliner I thnk) had Viewliners, of course.
I don't think the Metroliners were faster than regular corridor trains just by missing out more stops.