Is the T10 foch and the T9 foch armour any different ?
Has the track traverse speed of the 155 been nerfed with the engine power ?
No.
No but also yes.
Aside from crew skill the turning speed relies on traverse speed and engine power to weight. The better the ratio the faster the turning speed is reached. Consider turning speed as maximum top speed, the better your power to weight the easier you hit it.
So no, traverse stats have not changed but due to the engine nerf it will take longer for it to reach that maximum turning speed so in effect turning has been nerfed. Along with ability to reach top forward and reverse speed.