The Erie (AMC) S-class engines were considerably larger than NKP. Erie you may remember had clearances sized for the original 6' gauge so the engines could be bigger.
There is little comparison between the first generation of 'Super-Power' Berks and the Erie locomotives and subsequent engines derived from them (for example, if I recall correctly, the C&O T-1 2-10-4, which bears the same relationship to an S-class that the PRR Q1 was supposed to have to an M1: a "5/4" scaling up for that much more capacity).
The Erie engines were the first that were explicitly built for high road speed, and that design philosophy carried over into the Nickel Plate versions. Of course, if you used all the additional sophisticated improvements between the late '20s and the late '40s and applied it to a locomotive that was Erie-sized, you'd have a locomotive bigger and more powerful in proportion...
B&M didn't bother with evolving sophisticated 2-8-4s; they went instead to the most beautiful of all 4-8-2s (so good, in fact, that they got names like the 3713's class of beautiful Pacifics had). The B&M T class, even correcting for the Grim Reaper feedwater heater, ran not like a greyhound, but a more plebeian kind of dog - here's a picture that makes one look about as good as humanly possible
Compare them with this:
Some of the Ts were foisted on Southern Pacific for wartime service, and I seem to remember they weren't particularly liked there, either, but they apparently lasted long enough to be converted to oil firing in 1950 -- past the time the conversion could be excused as a response to the threatened coal strike. ATSF had at least one (of the seven they got) that was noted as lasting to 1955.
steamlocomotive.com has both the T1a and T1b at the same TE: 76160# (with boiler pressure 240# nominal, 63" drivers, 28x30 cylinders, and an almost frightening 3.44 FA) Reading between the lines, I smell booster. I also don't see any hard evidence that advanced balancing a la T&P 610 was done on any of the Ts, although that would have made them far more capable in general service for a fairly small investment...