So we are considering Pacifics now. Lots of railroads used them in passenger service. The Lehigh Valley used fat-boilered Pacifics in freight service.
Here's a light Pacific, Reading & Northern 425 at Jim Thorpe
Here is a heavy Pacific for comparison, Southern Ps-4 1401 in the Smithsonian
Just for fun I'll add No. 17, the YORK, running on the Northern Central between New Freedom and Hanover Junction. Her prototype, the LEVIATHAN, is joining her this week. For details, go to www.steamintohistory.com. No. 17 rolled out of Kloke Locomotive Works, Elgin, IL, in May, 2013!
Come to think of it, No. 17 would stand out among Acelas, Northeast Regionals, Keystone Service trains, and other arrivals and departures at Newark, NJ, or 30th Street Station. She now has a matching combine and coach built by the Reader Railroad in Arkansas now. Photos are posted at Facebook under Steam into History.