I'm not an expert but I imagine this sort of stuff would be less related to the loading gauge and more the electrical engineering side of things such as the different voltages of overhead lines on the continent, which can vary between 3kv to 15kv to even 25kv all for one unit, as well as the different propulsion systems. Continental Pendolinos also used different traction motors. The CD 680 traction system (which is 490kw rather than the 500kw you mentioned) uses phase fired thyristor control. The three-car Renfe Class 490 uses 4 asynchronous three-phase electric motors while the ten-car Alfa Pendular uses 8. By contrast the Class 390 uses Alstom's Onix drive system to control 12 traction motors. I can't say whether or not they are different enough to be factors in the different traction motor rating of each train, but I would be surprised if this combined with the different overhead line specifications for different Pendolinos didn't at least play a part in it.