If LHB coaches have little bit more weight it is not a problem, loco has enough power to haul it (although the additional power is undesirable). In trials loco horse powercapacity was not fully utilized.
Talgo can run at 20-25% higher speed at curves than LHB coaches. If speed restriction at curve is 50 kmph for LHB train, it will be eased to 60-62 kmph for Talgo. Even Talgo hasto reduce speed at curves.
India will be getting much more advanced Japanese Shikanshen Bullet Train Technology in next 7-8 years through Mumbai-Ahmedabad...
more... Bullet Train Project, a lot of thinking is required for final go ahead in mass procurement and construction of Talgo trains in India.