The original poster asked about ride quality back in the days when trains were operated with heavyweight equipment.
I'm one who rode, in my childhood, annual transcontinental trips between 1947 - 1955, nine total such trips, with 8-10 days aboard the train on a typical 2-3 week trip. So, I spent many weeks aboard Pullmans, going seemingly everywhere on those trips.
One has to remember that things were very different in those post war years, railroads were generally maintained to a high standard, as was the passenger equipment, so smooth riding was to be expected, and was delivered.
Being passholders, we rode the secondary trains, which, in those years were still provided full service, with dining and lounge service , and we had the blessing of Pulman passes during those years.
My perch, was the upper berth....though many nights I was allowed to occupy the lower while my parents visited the lounge for nightcaps. I'd fall asleep in the lower and never wake up until the next morning in the upper.
To this day I regard the sound of 6 wheel trucks, on jointed rail, to be the standard by which all other railroad truck sounds will be measured.