I agree…
with the comments above, I have had experience of a carbon wrapped seatpost, and it was not great. The carbon wrap is very thin, and is very easily distorted when clamping it in the seat-tube. You don’t get any benefits, but do get the frailties of both due to the thinness of the material used.
For the most part carbon stems seem to be heavier than the equivalent ali ones, and are more flexible.
I’d go for a full carbon seatpost and bars and a good alloy stem.