My two pennies: string tension is an important factor, and not all guitars are built equal; some require higher tension to sound well, some require lower tension. Also mixing different strengths is no sin; Savarez offers eg. a mixed set with high tension carbon trebles and medium tension basses. By carefully choosing the tensions of the strings one can equalize the sound quite a bit, at least volume wise. You'll have to experiment a bit.
Also the response might depend on the age of the instrument and how much it has been played. If you play a lot and with the right strings, it might improve anyway.
Sustain is another matter; my experience is that carbon trebles increase sustain quite a bit (this is also the case on all Stenzel guitars I know).
That has maybe not only to do with the flexibility but also with the internal damping of the material in case. The connection between pitch, mass and tension is a bit more complex (see eg. http://hyperphysics.phy-astr.gsu.edu/hbase/waves/string.html
; BTW on that page there is an important remark about the eddect of stiffnes), but you can see that the mass, length and tension is in there, so to achieve a certain pitch at a certain string tension and length, you need to have the same mass. Because carbon is denser, the strings are thinner, but the resulting mass is the same.
Music is a big continent with different landscapes and corners. Some of them I do visit frequently, some from time to time and some I know from hearsay only ...