Comparing British engines with US designs, the US designs always have "longer boilers"... but that may be an optical illusion if they are smaller diameter... I assume possibly because the fuel, being wood in the US, needs a much larger grate and firebox? (This was the reason for the US designed 4-4-0 locos having such a large firebox). And possibly larger flues to avoid soot build up from the wood resins? hence the flues need to be longer to be more efficient at capturing the heat? Coal being a relatively cheap fuel and readily available in the UK around the era when British Makers were making these engines, probably meant the flues tubes were smaller and got their efficiency that way and boilers were shorter as a result? Does anyone know the whys and wherefores?
Your observation is not an illusion. I've got a Plastow Burrell and it has a shorter boiler than my friends Case in the same scale. American engines did not always burn wood although they could. They burned the straw in large quantities when running a separator. The straw can't be used as feed so the threshers just burned it in the engine and it takes a lot of straw to fire a TE. Seems to me in the UK, traction engines burned coal. They may have here too , especially when plowing or pulling. The railroads used up a lot of wood and didn't leave much for anybody else.
A high-pitched screech? - Unfortunately, sound relies upon wavelength - which doesn't scale and make the same pitch. Wavelength is usually the length of the tube, or twice that length. Many lads with steam railway locos run the working whistle along a chassis rail to take advantage of the length - which would look stupid on top of the boiler. So the device on top of the boiler is inert (usually solid) just for show. That way the loco looks and sounds correct.