I have a set of the 15" / 16" cars in Erie Lackwanna from the late 80's that have the color window inserts. I picked the set up at auction without paying attention and the couplers have zinc rot on some of the cars. Just something else to be aware of.
I also have a set of Frank's Hobby House ones of the same size in the white 5 car set box from a few years after than in CNJ paint and they have never had any problems.
As for the 20" cars, I had an opportunity to buy a set of C&NW ones at a TCA auction about 4 years back. They are noticeably larger than the Lionel or K-line "scale" heavyweights. I passed for some reason I can't remember as I do like my scale length cars.