Passenger locos had taller drive wheels. Because having fast speeds to go, the rotation of the wheels could not be set over some limits. This depends on the bearings and thus the crank pin setup.
So tall wheels and a close to center crank pin reduces the rounds per mile, thus the rpm for higher speeds is reduced - and thus the piston has to travel lass fast the distances in the cylinder, so lower cycles appear, making the entry and exhaust of steam easier to handle.
That's why you see huge express engines having large diameter drive wheels.
On the lower diameter freight engines the crank is more to the outside of the wheel, and so you get a better crank angle and lever - thus more power is generated and the traction significantly increased.
A challenger runs with 1750 mm drivers as fast as a bavarian S3/6 - about 120 km/h.... but the engine of the challenger is a freight setup, thus: More traction, more rotation, more power... even two S3/6 won't match up one Challenger
The 844 hat a 2000 mm driver, thus will hold the 120 km/h (74,5 mph) much better and with less rpm than the challenger, thus the boiler hasn't the delivery need of so much steam, so is more economically - and you have a little of sprint abilities left... thus in 120 km/h the piston of the Challenger has to travel faster and making more distance, than those of the 844...
This is serious, because to piston represents an important mass going forwards and backwards, resulting in a swinging, wave like motion of the engine... Results are waving and wanking of the engines, disliked by most designers... and as more revolutions you have and as more powerful the gear is - like in freight locos - as more those motions disturb the smooth glide of the engine. Also the larger wheels give a more and better track stability, because exhibitin a better gyroscopic stability, that the smaller wheels.
Also the faster piston motion is more difficult to handle, because exhaust and entry timing are more difficult and the lubrication can get tricky...
We can simply say, that some of the modern northerns, with their 4-8-4 wheel set made the best all purpose locomotives, exhibiting good speeds and good tractions power, because of four driver axles and usually a good speeding ability.
Wheel, the leading truck or leading axle depends on how this is arranged. For most freight train locomotives, the engine does not have those fast speeds to go, so a leading truck isn't necessary and later modern steering arrangements, like the Krauss-Helmholtz steering axle, gave a very good ability on higher speeds and even narrow curves, without having the engines to get in traction powers in curves.
In the former Bissel axle, the leading wheels shift the frame only, thus the first drive wheel runs very roughly on the inside of the track, resulting in high forces and a minimation of tractive efforts on this axle - this was avoided by the Krauss-Helmholtz steering.
Locomotives with many driving wheels in Germany used later the Schwartzkopff-Eckhardt-steering gear, which was an improvement of the Krauss-Helmholtz steering gear... So the later came more with freight and narrow gauge steam engines - the Krauss-Helmholtz on passanger locomotives.
Express engines used the leading trucks, because the truck gave a more smooth control in curves, especially on high speeds. Thus the leading and steering of the frame in curves was taken by the first axle of the truck, shifting the truck and giving a good steering force to the frame, so here steering gear were not need, also the trucks exhibit the ability to include extra air brake cylinders, increasing the brake power of the engines, important on high speed safety reasons. Also the leading truck is much better for weight purpose, as the cylinder and front boiler loads can be better taken by the trucks, as for an single axle.
Thus... construction of a steam engine depends on what you want to do with... and a sportscar isn't a car a ranger will choose for his duty... and a cross country car isn't a choice for a racecar driver to go on the track.
So you design the locomotive for the purpose - and for this you choose axle arrangement and leading truck/axle set as well as wheel diameter...
Even today, there is no one for all purpose locomotive, even it's more easy with modern electric traction, to get close to this "one locomotive all purpose"....
Allways keep two-thrid level in gauge and a well set fire, that's how the engineer likes a fireman