Carbon seatpost clamp and carbon FD hanger, r they safe to use?

[takashi24]

For me, the weight is not much of the issue, but the design and simplicity of the clamp is much better than the metal alloy versions.

Couldnt agree more. The same reason I getting them myself

[MayhemSWE]

One last question. Is the FD clamp diameter same as the seatpost clamp diameter?

There is no general rule. Some frames will use a straight gauge seattube, others a tapered tube. If you don't know for sure you really need to measure with a caliper.