This question is spurred on by some observations I have made. When I was in New Mexico last summer I had the chance to help construct a section of rail to be accurate to the early 1910s. On the straightaways each rail was held down by two spikes diagonal in the tie plate. The historical actors said that this was the norm at the time for straightaways, curves would use three or four spikes depending on the tightness of the curve. When I was a school trip to Auschwitz and a few other Nazi concentration camps, I noticed that their rails were held by a mixture of spikes and bolts. There were also three spikes or bolts to every tie plate with only three places for a spike or bolt, unlike the four spaces in the tie plates I saw in New Mexico. Is there a specific reason why these changes happened in the 30-40 years between the construction of the railroads in New Mexico for logging and the railroads in Europe for the transportation of detainees?
Two on the straightaway, four on the curves, is normal American practice on all railways. American rr rarely use bolts: spikes are cheaper, faster to place. Bolts are a European practice, neither more or less advanced, just different. Bolts make repairs easier, since pulling a spike usually requires replacing the tie.
Do note that European equip't and loads are notably lighter than American, and they generally use lighter rail.