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There are two problems that trains face at curves. One is the problem of enough centripetal force, that is tackled by having a tilted track at curves. This is something that even a single coach traveling alone will face at curves.
But there is another problem that pops up only when the are multiple coaches involved. Normally, when a train is running, each coach experiences two forces through its couplers. One is a forward pulling force by the coaches in front, the other is a backward pulling force by the rear coaches. When the loco generates enough traction, the forward force dominates and the train moves forward.
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On straight tracks, these forces are aligned with the tracks and the direction of motion of the train, so they do not cause any lateral forces. But on curves, the shell of the coach remains in a straight line, while the bogies rotate and follow the curve. So these forces are no longer in a straight line and effectively it results in a lateral force that pulls the coach towards the inner edge of the curve. ( I highlighted this in the rather poorly drawn diagram with the red arrow as the effective force).
The longer the coach is, the more this force will be and to meet high speed requirements, the curve has to be made less sharp. This is why LHB coaches will need a lot of track upgrades to be able to run at higher speeds with long rakes.
Talgo on the other hand, uses a Jacobs bogie arrangement and several innovative facilities that reduce the impact due to this force on curves and hence, can hit higher speed on curves even with longer rakes.
The locomotive is not a factor in this problem and as long as it can hit the necessary speed, it is enough.