If arms race begins, adding a bomb would be much cheaper than a silo, so that’s not a good idea to simply expand the scale of silos for survivability.And China is not gonna end up with only 350 silos either. US alone has 450 Minuteman silos in active, I see no reason why China should not seek parity in silos with US.
New START Treaty expires on 2026 at which point China should have completed build-up and load-up of all 350 silos. It gives China a favorable position to negotiate a trilateral treaty with US and Russia in term of nuclear arm control.
I mentioned 2024 mostly because of Trump, and for START negotiation, we know little about Chinese attitude and let’s see what will happen then.